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Comrex Corporation

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DH20/22 Product Manual

About Comrex

Comrex has been building reliable, high quality broadcast equipment since 1961. Our products are used daily in every part of the world by networks, stations, and program producers.

Every product we manufacture has been carefully designed to function flawlessly, under the harshest conditions, over many years of use. Each unit we ship has been individually and thoroughly tested. Most items are available off-the-shelf, either directly from

Comrex or from our stocking dealers.

Comrex stands behind its products. We promise that if you call us for technical assistance, you will talk directly with someone who knows about the equipment and will do everything possible to help you.

Our toll free number in North America is 800-237-1776. Product information along with engineering notes and user reports are available on our webstite at http://www.comrex.com.

Our E-Mail address is [email protected]

Warranty and Disclaimer

All equipment manufactured by Comrex Corporation is warranted by Comrex against defects in material and workmanship for one year from the date of original purchase, as verified by the return of the Warranty Registration Card. During the warranty period, we will repair or, at our option, replace at no charge a product that proves to be defective, provided you obtain return authorization from Comrex and return the product, shipping prepaid, to Comrex Corporation, 19 Pine Road, Devens, MA 01434 USA. For return authorization, contact Comrex at 978-784-1776 or fax 978-784-1717.

This Warranty does not apply if the product has been damaged by accident or misuse or as the result of service or modification performed by anyone other than Comrex

Corporation.

With the exception of the warranties set forth above, Comrex Corporation makes no other warranties, expressed or implied or statutory, including but not limited to warranties of merchantability and fitness for a particular purpose, which are hereby expressly disclaimed. In no event shall Comrex Corporation have any liability for indirect, consequential or punitive damages resulting from the use of this product.

Copyright Notice

The Comrex proprietary code and licensed, third party proprietary code residing in and otherwise associated with this product are protected by copyright law and international treaties. Unauthorized reproduction or distribution of this product, or any portion of it, may result in civil and criminal sanctions, and will be prosecuted to the fullest extent of the law.

US Government Restricted Rights - Use, duplication, or disclosure by the US Government is subject to restrictions set forth in subparagraph (c)(1)(ii) of the Rights in Technical

Data and Computer Software clause at DFARS (48 CFR) 252.227-7013 or subparagraphs

(c)(1) and (2) of the Commercial Computer Software-Restricted Rights clause at FAR

(48 CFR) 52.227-19, as applicable.

3

Comrex Corporation

s eCtion

1. i ntroDuCtion

4

W hat iS a

h ybrid

?

Simply put, a hybrid is a device that separates send and receive audio on a phone line. While the public switched telephone network utilizes separate channels for audio in each direction of a phone call, these two signals are mixed together before being sent to the end user. This way, only one pair of wires is required from your telephone to the telco central office. To use telephone company terms, the telephone network is a “4 wire” system, while the local loop is a “2 wire” system.

When recording or airing telephone conversations in a studio environment, it’s important that telephone audio be “4 wire.” This is because the audio program usually already contains the audio of the “studio host.” If the telephone audio also contains some of the “studio host,” these two signals will be added together by the mixing console. The effect will be distortion in the voice of the “studio host.” In essence, a hybrid converts the “2 wire” telephone line back into a “4 wire” audio path.

It seems counter-intuitive, but the main goal of a studio hybrid is to make the people in the studio sound better. If the hybrid isn’t working well, people speaking from the studio will sound “hollow” or like they’re “talking into a barrel.” This is due to the strange effect of mixing microphone audio with telephone “bleed-through.” Of course, our hybrids also improve the audio of callers, filtering out hum and noise as well as adjusting levels between loud and soft speakers.

It’s our opinion that with the advent of cheap telephones, cordless phones and cellphones, telephone audio has gotten decidedly worse in recent years.

While a hybrid can cleanup noise to some extent, it can’t remove distortion caused by the far end telephone. If you find some calls sound good on air and some don’t, it’s probably due to the large disparity in audio quality of today’s telephone sets.

The DH20 and the DH22 digital telephone hybrids will help bring uniformity and high quality sound to a broadcast talk show environment. These digital hybrids provide a telephone interface between a telephone line and audio equipment.

The DH20 and DH22 use digital signal processing (DSP) technology to continually adapt to telephone-line conditions — providing consistent highquality sound and send to caller separation. The DH20 is a single digital hybrid, allowing connection of one telephone line for on-air use. The DH22 is a dual digital hybrid, allowing the connection of two telephone lines for on-air use.

When connected in accordance to United States, Canada, United Kingdom and mainland Europe compliance standards, the digital hybrids are perfect for your telephone application.

DH20/22 Product Manual dh20/22 F eatureS

W hat

c omeS With the dh20 or

dh22?

♦ Crystal clear, consistent audio quality

♦ Continual adaptation to telephone line conditions

Selectable automatic mix-minus and caller automatic gain control (AGC)

1W power amp with volume control on front-panel

Selectable mic/line level input

♦ On/Off control via front panel and rear panel remote connection

Analog receive filter for telephone line noise reduction

Selectable caller control (ducking)

Balanced inputs and outputs

Auxiliary output for recording

Simple installation and operation

Adjustable send/caller audio level control

Selectable single-ring auto-answer and auto-disconnect

Ensure that the following items were received with your shipment:

DH20

Volume

Calle r

Send

On Of f or

Volume

Send

Hybrid 2

Calle r

On Of f

Send

Hybrid 1

Calle r

On

Of f

DH22

(Domestic, Pan European or Australian)

P roduct

r egiStration and t echnical

S uPPort

7-foot Modular

Telephone Cord

Specialists in Remote

Audio

Transmission

DH20/22

Digital Telephone Hybrids

Product Manual

DH20/22

Product Manual

Please register your DH20/22 by filling out and returning the enclosed warranty registration card or by visiting www.comrex.com/warranty.htm. When your product is properly registered, Comrex can better serve you should you require technical assistance or need upgrades or new product information. If you have any problems or simply need a question answered, please call us at

978-784-1776. Our toll free number in North America is 800-237-1776. Product information along with engineering notes and user reports are available on our website at www.comrex.com. Our email address for technical support is [email protected]

5

Comrex Corporation

s eCtion

2. p roDuCt

D esCription

6

dh20/22 dh22 t elePhone

(n ull

)

S eParation

The DH20 and DH22 provide superior analog telephone integration into broadcast applications. With a variety of selectable functions from the front panel DIP S wItcheS

, these digital hybrids can be customized to meet your specific needs. By continually adapting to telephone line conditions and isolating send audio from caller audio, the DH20 and DH22 produce clean, consistent audio. Both hybrids offer a built-in mix-minus feature for installation when no mix-minus facilities are available through the console.

The DH22 is a dual hybrid unit designed for conferencing two telephone lines.

The DH22 has all the same features as the DH20 but can handle two callers at the same time. The two internal hybrids contain a common send audio input and the two telephone lines are internally conferenced. This means two callers can be on-air at once. Both callers’ audio can be combined as a single input on your console or as two separate outputs to two console inputs.

Using Digital Signal Processing (DSP) technology and firmware, the interface between a standard analog POTS line and your audio equipment will result in superior quality audio. The primary function of the DH20 and DH22 hybrids are to maximize the null by maximizing the separation of send and caller audio. Both hybrids provide >55dB null between 250Hz to 3.5kHz.

a utomatic

g ain

c ontrol

(agc)

AGC normalizes the gain of caller audio, augmenting the level of “soft” callers, and attenuating the level of “loud” callers. This helps provide more uniform caller audio levels at the caller output of the hybrid. The AGC threshold is

-50dBm. The AGC works to achieve an equivalent average caller level of

-30dBm from the telephone circuit.

a utomatic

m ix

-m inuS

The DH20 and DH22 auto mix-minus creates a mix-minus for the hybrid when one is not available from the audio console. See the “Mix-Minus” section on pages 13-16 for additional information.

c aller

c ontrol

Caller control, also known as ducking, attenuates the caller input audio when send audio is present. The purpose of this attenuation is to allow the talent to dominate their conversation with the callers. The amount of caller control

(attenuation) applied to the caller audio is selectable from 0 to 18dB, in 6dB increments.

s eCtion

3.

DH20/22 Product Manual

D iagrams anD

D esCriptions of

C ontrols anD

C onneCtors

F ront

P anel

c ontrolS

DH20 Front Panel Controls

1 2 3 4 5 6

4a

DH22 Front Panel Controls

7a 8a 9a10a

Send

Hybrid 2

Caller

On Off

11a 12a

7 8

Send

Caller

9 10

On Off

DH

20

11 12

Send Caller

Hybrid 1

On Off

DH

22

1) S

2) a

3) a

4) c

4 a

) S econd

c aller

o ut

5) diP S

WitcheS

6) v

7) S end ux ux aller olume end

i

S

o n end ut

o ut

led

This trim pot adjusts the level of audio sent to the phone line via the S enD

I n jack. At its midpoint (6 o’clock position), this trim pot is set for nominal send level (0dBu).

This trim pot adjusts the level of the auxiliary send audio coming from the

R emote

connector input and going onto the telephone line to the caller. At its midpoint (6 o’clock position), this trim pot is set for nominal level (0dBu).

This trim pot adjusts the level of the audio at the A ux

o ut

jack. At its midpoint

(6 o’clock position), this trim pot is set for nominal level (0dBu).

This trim pot adjusts the caller audio level to the user’s equipment. At its midpoint

(6 o’clock position), this trim pot is set for nominal caller level (0dBu).

The DH22 has a second c

AlleR

o ut

trim pot for hybrid 2.

These switches configure the hybrid’s system. Individual switch functions are defined in the “Calibration” section, starting on page 17.

These up/down buttons control the audio level of the monitor out speaker amplifier. Pressing a button once changes the level by 1dB. Pressing and holding a button sweeps the level up or down.

This bi-color LED indicates the relative level of the send audio into the digital hybrid. Green indicates nominal level, amber indicates caution and red indicates clipping.

7

8

Comrex Corporation

7

8

9 a

8) c a

) S

9) o a

10) o

10

11

) S

) S a a econd aller econd n econd

) S

11) o

) S

12) o

led

FF

S

led

c

o

led econd n

FF

S econd

S end

led aller n

o

Witch

o

Witch

led

FF n

led

led

S

Witch

12 a

) S econd

o

FF

S

Witch

The DH22 has a second S enD

LED for hybrid 2.

This bi-color LED indicates the relative level of the caller audio from the telephone line. Green represents nominal level, amber indicates caution and red indicates clipping.

The DH22 has a second c

AlleR

LED for hybrid 2.

This LED indicates that the DH20/22 has connected with the phone line. The

LED illuminates green when the hybrid is on and flashes green when the phone line is ringing.

The DH22 has a second o n

LED for hybrid 2.

This LED indicates the hybrid is not connected to an active phone line. The

LED illuminates red when the hybrid is off.

The DH22 has a second o ff

LED for hybrid 2.

The o n

switch connects the hybrid to the telephone line.

The DH22 has a second o n

switch for hybrid 2.

The o ff

switch disconnects the hybrid from the telephone line and mutes all audio going to and from the telephone line.

The DH22 has a second o ff

switch for hybrid 2.

DH20/22 Product Manual r ear

P anel

c onnectorS

DH20 Rear Panel Connectors

DH22 Rear Panel Connectors

a a

1) P

2) r

3) m

4) S end

5) c aller

o ut

5 a

) S econd

c aller

o ut

6) a ux

o ut

7) l

8) S

8 a ine et

) S oWer emote onitor

i n econd

o

S ut et

The AC power cord input is an IEC type connector allowing use of premolded domestic US power cords as well as various other premolded international power cords.

This DB25 female connector provides remote control and status of the hybrid.

Unbalanced send in, caller out and aux out audio are also available at the R emote connector. See “Pinouts” on page 26.

This 1/4” jack is a speaker connection for monitoring the caller audio signal.

The monitor output provides 1 Watt into an 8 Ohm speaker.

This balanced, female, 3-pin XLR input receives audio from the source

(microphone or mixer) and sends it to the caller. Note: if using a single

microphone that needs phantom power to operate, you must supply this power

to the microphone. The digital hybrid does not supply phantom power. Audio sent to the caller must be a mix-minus. (See the “Mix-Minus” section on pages

13-16.)

This balanced, male, 3-pin XLR output contains the audio from the caller.

The DH22 has a second c

AlleR

o ut

for hybrid 2.

This balanced, male, 3-pin XLR output contains a mix of caller and send audio or caller audio only. (See “DIP Switches” on pages 17-19.) This connector can feed a recording device to record both the caller and send audio.

This RJ11 connector provides connection of the telephone line to the hybrid.

A-Lead closure is provided (see page 27 for further details).

This RJ11 connector allows connection to a standard analog telephone set. The telephone line is present at this connector when the hybrid is off. The telephone line is not present at this connector when the hybrid is on. A-Lead closure is provided (see page 27 for further details).

The DH22 has a second l

Ine

and S et

pair for hybrid 2.

9

10

Comrex Corporation

s eCtion

4. i nstallation

t r elePhone

l ine equirementS i nStallation

e xamPleS

The DH20/22 operates on a standard POTS (plain old telephone service) analog telephone line or an analog extension from a PBX via a standard RJ11 modular jack. Note: Some telephone lines do not provide battery voltage (dry

line, no DC offset voltage). If yours does not, the DH20/22 may be configured by qualified personnel for dry line operation. Please contact Comrex

Technical Support for details.

The hybrids are designed for easy installation and set up. All necessary interface connections are made through rear panel connectors. Refer to “Rear

Panel Connectors” on page 9 for a description and placement of each of the connections you will be making.

The diagram below illustrates typical hybrid connections for the DH20.

To install your hybrid, make the following connections:

Typical DH20 Installation

Console In

Mix-Minus Out

Telephone Line Telephone Set

SEND IN CALLER OUT

AUX OUT

Record Input

DH20/22 Product Manual

The diagrams below illustrate typical hybrid connections for the DH22:

Typical DH22 Installation — Independent Callers

Telephone

Set

Console Out

Telephone

Line 1

Telephone

Line 2

Telephone

Set

SEND IN

CALLER 1 OUT CALLER 2 OUT AUX OUT

Caller 1 & Caller 2

(See page 19 for setting DIP S wItch

11 which enables/disables Caller Mix)

Typical DH22 Installation — Callers Mixed

Console Out

Caller 1 & 2 Mixed

SEND IN

CALLER 1 OUT CALLER 2 OUT AUX OUT

Caller 1 & Caller 2

11

Comrex Corporation

12

P oWer

c onnection r emote

c ontrol a udio

c onnectionS t c elePhone

l onnectionS ine

The DH20/22 will operate with any power source between

100-240VAC, 50/60Hz.

If using a remote control for parallel control and hybrid status, use the DB25 R emote

connector. For “Pinouts,” see page 26.

Monitor Out — This 1/4” TRS jack provides a 1W amplified caller signal into an 8 Ohm speaker.

Send In — Connect the S enD

I n

female XLR jack to an output from your studio console. When the hybrid is on, the audio connected to this input will be fed onto the phone line. Audio sent to the telephone line must be a mix-minus.

See the “Mix-Minus” section on pages 13-16.

Caller 1 and 2 Out — Connect the c

AlleR

o ut

male XLR jack(s) to the input(s) on your audio console. When the hybrid is on, this output will contain the audio coming from the caller(s). The DH22 caller out audio may be configured for a mix of caller audio on c

AlleR

1 o ut

or independent caller audio on c

AlleR

1 o ut

and c

AlleR

2 o ut

. See “DIP

Switches” on pages 17-19.

Aux Out — Connect this male XLR jack to your recording device. The A ux

o ut

can be configured to contain a mix of send audio and caller audio or caller audio only. See “DIP

Switches” on pages 17-19.

Telco 1 Line — Plug your analog telephone line into the

RJ11 l

Ine

jack.

Telco 1 Set — Plug your telephone set into the RJ11 S et jack.

Telco 2 Line (For DH22) — Plug your second analog telephone line into the RJ11 l

Ine

jack.

Telco 2 Set (For DH22) — Plug your second telephone set into the RJ11 S et

jack.

TELCO 1

LINE SET

TELCO 2

LINE SET

GND

GND

DH20/22 Product Manual

s eCtion

5. m ix

-m inus

u

Sing the

m ic

P reamP

Mix-minus is a mix of all studio audio sources except caller audio. Without a mix-minus feed from the console, the caller audio sent to the console will be retransmitted to the caller. This can cause hollow sounding audio and can even result in feedback. The diagrams in this section illustrate some of the ways to create/configure an external mix-minus feed for the DH20/22 hybrid.

The internal mix-minus feature in these hybrids can be effective in removing the caller from the outgoing audio feed (the feed being sent back down the phone line). It does have its limitations, however. Because this mix-minus generation works on the same principles as the send-receive separation, changes in program level (e.g. riding a fader on the console) will cause the mix-minus feed to adapt, causing performance issues and audio distortion.

The mix-minus generator is also very sensitive to non-linear processing (mic processors or compressor-limiters), so these must be left out of the signal chain. For the same reason, the mix-minus generation will cause severe distortion on over driven audio levels.

In practice, whenever practical, we recommend creation of a true mix-minus feed in the studio rather than engaging this function. We consider this feature useful as a last resort, when no true mix-minus is technically possible. If an external mix-minus cannot be obtained, then activate the DH20/22’s internal mix-minus feature. See “DIP Switches” on pages 17-19.

If only microphone audio is being sent to the caller, the internal microphone preamplifier of the hybrid may be used. When doing this, change the S enD

I n

jack from a line level input to a mic level input by placing DIP S wItch

4 to the on (up) position.

Telephone Line

Send

Telephone Set

Microphone

Tape Player

13

Comrex Corporation

14

u

Sing the

d irect

m ic o utPut oF the

c onSole

If only microphone audio is being sent to the caller, then it is possible to use the console’s direct microphone output. Use the console direct microphone output to provide line level microphone audio to the S enD

I n

jack of the DH20/22.

Telephone Line

Send Caller

Mix -Minus

Telephone Set

Program Mix

Tape Player/Recorder

Transmitter

CD Player

Mix Output

Inputs

Console/Mixer

Microphone

Note: Microphone audio receives preamplification from the console.

u m

Sing a

d iScrete icroPhone

m ixer

If only microphone audio is being sent to the caller, a separate microphone mixer may be used. The mic mixer will provide the mix-minus feed for the hybrid, because its output contains no caller audio.

Telephone Line

Program Mix

Transmitter

Send Caller

Mix-Minus

Telephone Set

Tape Player/Recorder

CD Player

Mic Mixer

Microphones

Mix Output Inputs

Console/Mixer

DH20/22 Product Manual u

Sing an

i nternal

m ix b uS

(t elePhone

m odule

)

Many console manufacturers provide optional telephone hybrid modules for their consoles. These modules are designed to receive audio from a hybrid and transmit audio to the hybrid. A telephone module will create a mix-minus for the hybrid at its output.

Telephone Line

Program Mix

Transmitter

Send Caller

Mix-Minus

Telephone Set

Tape Player/Recorder

CD Player

u

Sing a

S m ix o utPut

b uS From the c onSole eParate

Mix Output

Inputs

Console/Mixer

Microphone

Note: The Telephone Module provides a mix-minus output.

If the console has an extra mix output, then use this extra output to provide a mix-minus feed for the hybrid. Simply route all audio, minus the caller audio, to the extra output bus of the console (Output B).

Telephone Line

Send Caller

Program Mix

Mix-Minus

Transmitter

Telephone Set

Tape Player/Recorder

CD Player

Output

A

Output

B

Inputs

Console/Mixer

ON

OFF

Microphone

Note: All input channels are selected to the Outputs A and B, except for the incoming caller audio. It is selected to

Output A only.

15

Comrex Corporation

16

u

Sing a

S eParate

a uxiliary o utPut

b uS From the c onSole

If the console has an auxiliary output, usually called Aux Out or Aux Send, then use this auxiliary output to provide a mix-minus feed for the hybrid. Simply route all audio, minus the caller audio, to the auxiliary output bus of the console.

Telephone Line

Mix-Minus

Send Caller

Telephone Set

Program Mix

Transmitter

Tape Player/Recorder

Mix

Output

Aux

Output

CD Player

Mix

Output

Auxiliary

Output

Console/Mixer

Inputs

Microphone

Note: All input channels have been turned up with the auxiliary level controls, with the exception of the incoming caller audio. Therefore the auxiliary output contains all input sources minus the caller audio.

u

Sing the

S tereo

o utPutS oF the

c onSole

By using the stereo outputs of the console, it is possible to create a mix-minus for the hybrid. By panning the caller audio to the left channel only, the caller audio is prevented from reaching the right channel output of the console. Therefore, the right channel output is a mix-minus - a mix of all audio minus the caller audio.

Telephone Line

Send Caller

Program Mix

Mix-Minus

Transmitter

Telephone Set

Tape Player/Recorder

CD Player

Stereo

Output

Inputs

Console/Mixer

Microphone

Note: The Incoming caller audio is faded to the left channel of the console's stereo output. This prevents caller audio from being returned to the send input.

DH20/22 Product Manual

s eCtion

6. C alibration

diP S

WitcheS

DIP S wItcheS

are “off ” in the down position and “on” in the up position.

6. CALLER CONTROL 2

5. CALLER CONTROL 1

4. MIC LINE

3. ON/OFF MODE

2. CALLER BOOST

1. BURST ADAPT

CALLER 1

OUT

CALLER 2

OUT

7. AUTO ANSWER

8. AUTO DISCONNECT

9. CALLER AGC

10. MIX-MINUS

11. CALLER 1 MIX

12. AUX MIX

DIP S wItch

1 — Enables/disables the Burst Adapt feature. In the “off ” position (down) the hybrid is in Auto Adapt Mode. In the “on” position (up) the hybrid will send a noise burst to the telephone line and aggressively adapt before returning to Auto Adapt Mode. Each press of the o n

button will generate a new noise burst.

In either mode, the hybrid continually monitors and adapts to the changing telephone line conditions in order to digitally cancel the telephone line echo and provide the best send-to-caller separation possible.

DIP S wItch

2 — Enables/disables the Caller Boost feature. In the “off ” position (down) the caller boost feature is disabled. In the “on” position (up) the hybrid adds 6dB of level boost to the caller’s audio at the c

AlleR

o ut

jack.

DIP S wItch

3 — Allows the hybrid to work with two types of switches for external (remote) control — momentary and latching. In the “off ” position

(down) the o n

/o ff

control inputs respond to momentary closures to ground.

This turns the hybrid on when it receives a momentary closure on the o n

control input and off when it receives a closure on the o ff

control input. In the

“on” position (up) the o ff

control input is disabled and the o n

control input responds to a latching closure to ground. This will cause the hybrid to turn on when the latching switch is closed to ground and the hybrid will remain on until the closure to ground is opened. This DIP S wItch

setting also affects the operation of the front panel o n

/o ff

buttons. See “Pinouts” (page 26) for

R emote

c ontRol

connector pinouts.

DH20

DH20

17

18

Comrex Corporation

DIP S wItch

4 — Sets the gain of the S enD

I n

jack. In the “off ” position (down) the input is a nominal line level (0dBu) input. In the “on” position (up) the input is a mic level providing +55dBu of input gain.

DIP S wItcheS

5 & 6 — Enables/disables the Caller Control (ducking) feature.

In the “on” position (up) the hybrid will provide caller control, which is the suppression of caller audio when send audio is present. In the “off ” position (down) caller control is disabled. DIP S wItch

5, when active, adds 6dB of caller control and DIP S wItch

6, when active, adds 12dB of caller control.

If both are active, then the sum of the two DIP S wItcheS

is used, and 18dB of caller control is provided.

DIP S wItch

7 — Enables/disables the Auto Answer feature. In the “off ” position (down) the hybrid will not automatically answer the telephone line. In the “on” position (up) the hybrid will automatically answer the telephone line after the first ring.

DIP S wItch

8 — Enables/disables the Auto Disconnect feature. In the “off ” position (down) the hybrid will not automatically disconnect the telephone line. In the “on” position (up) the hybrid will automatically disconnect the telephone line after the caller hangs up. Note: The telephone line must pro-

vide loop drop, loop reversal or call progress signals in order for the Auto

Disconnect feature to function. Most telephone systems will provide loop drop shortly after the calling party hangs up. Some PBX systems, but not all, will provide either loop drop or call progress tones such as reorder tones or busy signals. The hybrid will detect most of these signals and then auto disconnect the telephone line.

DIP S wItch

9 — Enables/disables the Automatic Gain Control (AGC) feature.

In the “off ” position (down) the AGc feature is disabled. In the “on” position

(up) the AGC feature is enabled. When enabled, the AGC feature normalizes the gain of the caller audio, augmenting the level of “soft” callers and attenuating the level of “loud” callers. This helps provide more uniform caller audio levels at the caller output of the hybrid. The AGC works to achieve an equivalent average caller level of -30dBm from the telephone circuit.

DH20/22 Product Manual

DIP S wItch

10 — Enables/disables the Automatic Mix-Minus feature. In the “off ” position (down) the Automatic Mix-Minus feature is disabled. In the “on” position (up) the Automatic Mix-Minus feature is enabled. When

Automatic Mix-Minus is enabled, it is not necessary for you to create a mixminus output with your console/mixer. You can simply feed program audio to the send input of the hybrid, and the hybrid will automatically remove the caller audio from the program mix and prevent it from returning to the caller as echo, which prevents possible feedback. Note: This option should

only be enabled when no mix-minus facilities are available through the console or mixer.

DIP S wItch

11 (DH22 only) Enables/disables the Caller 1 Mix feature . In the “off ” (down) position the Caller 1 Mix feature is disabled and telephone lines one and two will appear at the c

AlleR

1 o ut

and c

AlleR

2 o ut

XLR connectors respectively. This allows each caller to be routed to a separate input channel of a console or mixer. In the “on” (up) position the Caller 1 Mix feature is enabled and telephone lines one and two will be internally mixed by the hybrid and appear at the c

AlleR

1 o utPut

. This allows two callers to be routed to a single input channel of a console or mixer. Note: When Caller 1

Mix is enabled, the c aller

2 XLR is not active.

DIP S wItch

12 — Enables/disables the Aux Mix feature. In the “off ” (down) position, the A ux

o ut

and R emote

A ux

o ut

will contain caller audio only. In the “on” (up) position the A ux

o ut

and R emote

A ux

o ut

audio will contain a mix of send and caller audio.

19

Comrex Corporation t rim

P otS

The front panel trim pots provide level adjustments of the S enD

I n

, A ux

S enD

,

A ux

o ut

, and c

AlleR

o ut

audio connectors. Separate audio level controls let you optimize the audio level(s) of the DH20/22 to match the audio levels required by the interfaced audio equipment.

In order to optimize the audio levels, have someone call the hybrid from another location. Answer the line by pressing the o n

button and continue through the level adjustments. Be aware that some suppression and/or echo may be heard while calibrating the audio levels. Disregard it and continue until the end of the procedure. When the hybrid is properly calibrated there will be no echo or suppression.

20

S enD

I n

This pot adjusts the send in audio. Adjust this pot along with your console audio control until callers verify that the audio level they are receiving is at a comfortable listening level. With comfortable listening levels, the S enD

LED should illuminate solid green with an occasional flash of amber on audio peaks. If the S enD

LED illuminates red, the audio levels are clipping and should be decreased via the send level adjustments.

A ux

S enD

This pot adjusts the level of the auxiliary send audio at the R e

mote

c onnectoR

input. Adjust this pot along with your console audio control until callers verify that the audio level they are receiving is at a comfortable listening level.

A ux

O ut

This pot adjusts the level of send and caller audio at the A ux

o ut jack. Adjust this pot along with your console audio control to set the proper level for your recording device or other external devices.

DH20/22 Product Manual

c

Aller

1 O ut

This pot adjusts the caller 1 out audio. Adjust this pot along with your console audio control to set the caller’s voice/audio to a comfortable listening level.

c

Aller

2 O ut

This pot adjusts the caller 2 out audio. Adjust this pot along with your console audio control to set the caller’s voice/audio to a comfortable listening level.

Note: The c aller

trim pot has no effect on the c aller

LED. The c aller

LED indicates actual level from the telephone line only. If the c aller

LED flashes green only occasionally with caller audio, the level from the telephone line is too low and you should activate the c aller

b ooSt

diP S

Witch

. See “DIP Switches” on pages 17-19.

t raining the

t elePhone e cho

c anceller

Upon connection to the telephone line, the digital hybrid will automatically begin its telephone echo cancellation process. This will optimize the send to caller separation. If the send to caller separation is not sufficient, you may force the hybrid to “train” itself to the telephone line by pressing and holding the o n

button for one second. After one second, the hybrid will emit a burst of white noise. The noise burst allows the hybrid to aggressively adapt to the echo returning from the telephone network and allows the hybrid to maximize its send-to-caller separation.

This noise burst can be generated at any time by pressing and holding the o n

button for one second. To force a noise burst on every connection to the telephone line, activate the B uRSt

A

DAPt

DIP S wItch

1. See “DIP Switches” on pages 17-19.

t raining the

m ix

-m inuS

Upon connection to the telephone line, the digital hybrid will automatically begin its mix-minus echo cancellation processes. To verify/fine tune the calibration of the mix-minus, watch the S enD

LED as the caller speaks. If the S enD

LED is not lighting or only flashing green on the caller’s audio peaks, then the calibration is already complete. If the S enD

LED is lighting solid green on caller audio, decrease the loop gain via the S enD

I nPut

pot or the console level control and train the telephone echo canceller. As the caller continues to speak, you should notice that the S enD

LED will begin to illuminate less and less until it no longer lights green on caller audio. This process may need to be repeated if the desired results are not achieved or if the caller is complaining of excessive echo.

21

Comrex Corporation

s eCtion

7. o peration

22

Front Panel

u

Sing the

h ybrid

Send

Caller

4 5

On Of f

DH

20

2 3

1

Press the o n

button (2) to connect the hybrid to the telephone line. Press the o ff

button (3) to disconnect the hybrid from the telephone line. Note:

The o n

and o

FF

buttons do not turn on/off the power to the DH20/22. They connect and disconnect it from the phone line.

DH22 users: Ensure that you press the o n

or o

FF

button that corresponds with the hybrid you wish to connect or disconnect. Also, when both hybrids are active in the o n

position, telephone callers will be conferenced internally by the DH22.

u

Sing the

t elePhone

S et

Lift the handset to connect the telephone to the telephone line. Hang up the handset to disconnect the telephone from the telephone line.

S

Witching a

c all From the

S et to the

h ybrid

Press the hybrid’s o n

button (2). The active call will switch from the phone to the hybrid.

S

Witching a

c all From the h ybrid to the

S et

Make sure the telephone handset is off hook. Then press the hybrid’s o ff button (3). The active call will switch from the hybrid to the phone.

d iSconnecting a

c all

P lacing a

c all

To disconnect the telephone line, the hybrid must be off and the telephone handset must be hung up. If either the hybrid is on or the handset is off hook, then the phone line is still active.

Lift the handset and listen for the dial tone. Dial the party you wish to call. Talk to the caller with the telephone set or press the hybrid’s o n button (2) to talk through the hybrid. When finished, press the o ff button (3) and/or hang up the handset.

DH20/22 Product Manual a djuSting the

m onitor o utPut

l evel

To adjust the level at the monitor output, use the V olume

buttons (1). With each press, the V olume

button increases the monitor output level by 1dB. The

V olume

button decreases the monitor output level by 1dB. Pressing and holding the button will sweep the level up or down respectively.

r emote

c ontrol

o

Ption

The R emote

c ontRol

connector can be used to perform three functions: Moni-

tor Mute On/Off, Hybrid On, and Hybrid Off.

If using a remote control device, internal DIP S wItch

3 will select the type of button switch function you need (momentary or latching). See page 17 for further details.

DIP S wItch

3 does not change the operation of the monitor mute input. The monitor output will be muted for as long as the monitor mute input pin is tied to ground.

r ecording

o

Ption

While on a connected call, a mix of both send and caller(s) audio, or caller(s) audio only, will be routed to the A ux

connector. Connect your recording device to this connector. Activate the record function of the external recording device to capture the audio.

23

Comrex Corporation

s eCtion

8. s peCifiCations

24

F ront

P anel r ear

P anel

Controls:

Hybrid One On Button

Hybrid One Off Button

Hybrid Two On Button (DH22)

Hybrid Two Off Button (DH22)

Volume Up and Volume Down Buttons

Status LED’s:

On Status

Off Status

Hybrid One Send Audio Presence

Hybrid One Caller Audio Presence

Hybrid Two Send Audio Presence (DH22)

Hybrid Two Caller Audio Presence (DH22)

Adjustments:

Send Input Level

Caller One Output Level

Caller Two Output Level

Auxiliary Input Level

Auxiliary Output Level

DIP Switches:

Burst Adapt Selection

Mic/Line Selection

Caller Boost Selection

Momentary/Latching Control

Auto Answer/Disconnect Selection

Call Control Selection (0, 6, 12 or 18dB)

AGC Selection

Auto Mix-Minus Selection

Caller One Mix Selection (DH22)

Aux Mix Selection

Power: IEC Type

Auto Adjusting, 100-240VAC, 2A, 50/60Hz, 30W

Remote: DB25 Female

Send Input — 0dBu nominal, adjustable, unbalanced, 20k Ohm impedance.

Caller and Aux Outputs — 0dBu nominal, adjustable, unbalanced,

50k Ohm impedance.

DH20/22 Product Manual r ear

P anel

c ontinued

Control Inputs — Remotely activate any of the following functions with a switch closure to ground: Hybrid 1 o n

, Hybrid 1 o ff

, Hybrid 2 o n

, Hybrid

2 o ff

and Monitor Mute.

Status Outputs — Remotely check the status and audio presence of the hybrids using the Hybrid 1 and 2 o n

, o ff

, S enD

and c

AlleR

presence status outputs. Status outputs are open collector outputs rated 30VDC and

40mA maximum.

Monitor Output: 1/4” Stereo Jack

Tip = + phase, Ring = ground, Sleeve = ground

1W output into an 8 Ohm load

Send Input: XLR Female

Mic/Line selectable, -55/0 dBu nominal, adjustable, balanced bridging,

20k Ohm impedance

Caller 1 and 2 Outputs: XLR Male

0 dBu nominal, adjustable, balanced, 50 Ohm impedance

Aux Output: XLR Male

0 dBu nominal, adjustable, balanced, 50 Ohm impedance

Telco 1 and 2 Lines: RJ11 Connector

POTS (Plain Old Telephone Service) telephone line or analog extension from a PBX or dry line (no DC offset voltage). A-Lead Supervision provided

Telco 1 and 2 Sets: RJ11 Connector

A-Lead Supervision provided

t elePhone

t ranSmit t elePhone

r eceive

Nominal send input of 0 dBu referenced to -15 dBm onto the telephone line.

Frequency Response: +/- 1dB from 250 Hz to 3.5 kHz; Dynamic Range: >70dB;

Distortion: <0.2%

Nominal phone line level of -15dBm referenced to caller output of 0dBu.

Frequency Response: +/- 1dB from 250 Hz to 3.5 kHz; Dynamic Range: >70dB;

Distortion: <0.2%

25

Comrex Corporation

26

n ull m ix

-m inuS

P inoutS

Send-to-Caller Separation: 55dB

Tail Time: 32 milliseconds

Caller-to-Send Separation: 50db nominal

Tail Time: 32 milliseconds

Remote Connector Pinout:

12

13

14

15

16

17

18

19

20

21

22

23

24

25

Pin

1

2

3

4

5

6

7

8

9

10

11

Description

Remote Hybrid 1 On *

Remote Hybrid 1 Off *

Remote Hybrid 2 On *#

Remote Hybrid 2 Off *#

Switch/Indicator Common

Hybrid 2 Send Presence Indication **#

Hybrid 2 Caller Presence Indication **#

N/C

Unbalanced Send Audio Input (0dBu nominal)

Unbalanced Caller Audio Output (0dBu nominal)

Unbalanced Aux Audio Output (0dBu nominal)

Monitor Mute Control*

Audio Common

Hybrid 1 On Indication **

Hybrid 1 Off Indication **

Hybrid 2 On Indication **#

Hybrid 2 Off Indication **#

Switch/Indicator Common

Hybrid 1 Send Presence Indicator **

Hybrid 1 Caller Presence Indicator **

Switch/Indicator Common

Audio Common

Audio Common

Audio Common

Switch/Indicator Common

* Remote control provided via contact closure to Switch/Indicator

Common

** Remote indicators provided via open collector outputs to Indicator

Common (<15V, <39mA)

# DH22 only

DH20/22 Product Manual

Line Connector Pinout:

*

*

4

5

6

Pin

1

2

3

Description

To pin 6 of S et

RJ11

To pin 5 of l

Ine

Tip

Ring

To pin 2 of S et

To pin 1 of S et

RJ11

Set Connector Pinout:

*

*

4

5

6

Pin

1

2

3

Description

To pin 6 of l

Ine

RJ11

To pin 5 of S et

Ring

Tip

To pin 2 of l

Ine

To pin 1 of l

Ine

RJ11

* When the o n

button is illuminated on the DH20/22, an “A-Lead Closure” is provided between pins 2 and 5 of the l

Ine

and S et

jacks. This connection is useful for key telephone system such as the 1A2. If you connect the DH20/22 to an extension jack of a more modern PBX, you should first check to see if those wires are used for signalling or power. If so, do not connect them to the DH20/22. You may, however, use the pin 2-5 connection to control the hookswitch on a modified PBX phone. Contact Comrex Technical Support for more information.

27

28

Comrex Corporation

s eCtion

9. b loCk

D iagrams

dh20

DH22

DH20/22 Product Manual

29

Comrex Corporation

s eCtion

10. C omplianCe

30

Fcc P art

15 c omPliance

This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC rules.

These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communications.

Operation of this equipment in a residential area is likely to cause harmful interference, in which case the user will be required to correct the interference at his/her own expense.

Changes or modifications not expressly approved by Comrex Corporation could void the user’s authority to operate the equipment.

Fcc P art

68 c omPliance

FCC Registration Number: FBIUSA-31573-BR-N

Ringer Equivalence Number (REN): 1.1B

A label containing, among other information, the FCC registration number and Ringer Equivalence Number (REN) for this equipment is prominently posted on the top plate, near the rear of the equipment. If requested, this information must be provided to your telephone company.

USOC Jacks: This device uses RJ11 terminal jacks.

The REN is used to determine the quantity of devices which may be connected to the telephone line. Excessive REN’s on the telephone line may result in the devices not ringing in response to an incoming call. In most, but not all areas, the sum of the REN’s should not exceed five (5). To be certain of the number of devices that may be connected to the line, as determined by the total REN’s, contact the telephone company to obtain the maximum REN’s for the calling area.

If this equipment causes harm to the telephone network, the telephone company will notify you in advance that temporary discontinuance of service may be required. If advance notice is not practical, the telephone company will notify the customer as soon as possible. Also, you will be advised of your right to file a complaint with the FCC, if you believe it is necessary.

DH20/22 Product Manual ic c omPliance

The telephone company may make changes in its facilities, equipment, operations, or procedures that could affect the operation of the equipment. If this happens, the telephone company will provide advance notice for you to make the necessary modifications in order to maintain uninterrupted service.

If you experience problems with this equipment, contact Comrex Corporation, 19 Pine Road, Devens, Massachusetts 01434, or by telephone at 978-

784-1776 for repair and warranty information. If the trouble is causing harm to the telephone network, the telephone company may request you remove the equipment from the network until the problem is resolved.

No user serviceable parts are contained in this product. If damage or malfunction occurs, contact Comrex Corporation for instructions on its repair or return. This equipment cannot be used on telephone company provided coin service. Connection to Party Line Service is subject to state tariffs.

Ringer Equivalence Number (REN): 1.1

IC Certification Number: 1970 8175 A

NOTICE: The Industry of Canada label identifies certified equipment. This certification means that the equipment meets certain telecommunications network protective operational and safety requirements. The Department does not guarantee the equipment will operate to the user’s satisfaction.

Before installing this equipment, users should ensure that it is permissible to be connected to the facilities of the local telecommunications company.

The equipment must also be installed using an acceptable method of connection. In some cases, the company’s inside wiring associated with a single line individual service may be extended by means of a certified connector assembly (telephone extension cord). The customer should be aware that compliance with the above conditions may not prevent degradation of service in some situations.

Repairs to certified equipment should be made Comrex Corporation. Any repairs or alterations made by the user to this equipment, or equipment malfunctions, may give the telecommunications company cause to request the user to disconnect the equipment.

Users should ensure for their own protection that the electrical ground connections of the power utility, telephone lines and internal metallic water pipe system, if present, are connected together. This precaution may be particularly important in rural areas.

31

32

Comrex Corporation e uroPean

c omPliance

This equipment has been approved in accordance with Council Decision 98/

482/EC for pan-European single terminal connection to the public switched telephone network (PSTN). However, due to differences between the individual PSTN’s provided in different countries, the approval does not, of itself, give an unconditionally assurance of successful operation on every PSTN network termination point. In the event of problems, you should contact your equipment supplier in the first instance.

Comrex Corporation of 19 Pine Road, Devens, Massachusetts 01434, U.S.A. declares that this equipment is designed to be compatible with the following networks: Austria, Belgium, Denmark, Finland, France, Germany, Greece,

Iceland, Ireland, Italy, Liechtenstein, Luxembourg, The Netherlands, Norway,

Portugal, Spain, Sweden, Switzerland and United Kingdom.

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