Natural-sounding telephone audio... Hybrids

Natural-sounding telephone audio... Hybrids
Natural-sounding telephone audio...
... for broadcast, conferencing
and public address
About Comrex DH Series
Digital Telephone Hybrids
When you want to present, broadcast, or record a telephone conversation,
it’s important to separate the “send” audio from the “receive” audio on the
call. If proper isolation is not achieved, unpleasant things can happen to your
audio like echo, feedback, and the dreaded “barrel effect”. Hybrids are used
to convert the “two-wire” telephone network back into a “four-wire” circuit,
providing separate audio connectors for send and receive, and isolating the
two using digital signal processing. The Comrex DH Series Digital Telephone
Hybrids also provide filtering of unwanted “hum” and “hiss”, as well as
automatically adjusting caller audio to a uniform level.
Comrex understands telephone-to-audio interface better than anyone else.
For 30 years we’ve been improving the sound of phone lines for broadcasters. The careful design of the Comrex DH Series results in consistent,
high-quality audio. Installation is rapid, adjustments are set-and-forget, and
operation is straightforward.
Select from one of three models to “answer the call” of your application:
• DH20 single hybrid unit with analog audio connections and the
quality you demand.
• DH22 dual-hybrid unit to connect to two phone lines simultaneously
for flawless conferencing.
• DH30 single hybrid unit with advanced audio processing for best audio
performance, both digital and analog audio connections
and a number of additional convenient features.
All models also include selectable automatic gain control (AGC) to keep
caller's audio level consistant, as well as caller ducking that lowers incoming
caller audio so local talent remains in control of the conversation.
Need telephone audio? Put Comrex on the line.
Features & Benefits
Digital hybrid and audio processing performance
• Comrex’s proprietary high-performance, digital hybrids deliver
consistently high quality telephone audio.
• Continuously adapt to telephone line conditions.
• Deep, stable hybrid null ensures maximum isolation between local
(send) and caller audio.
• Eliminates echo, “honking” and other artifacts.
• Receive filter reduces telephone line noise.
• Selectable AGC maintains a consistent audio output, even when the
caller signal varies widely.
• Selectable caller ducking lowers incoming caller audio so local talent
remains in control of the conversation.
Additional audio processing on the DH30:
• Acoustic echo cancelling for applications where open speakers
and microphones are used.
• Adjustable digital compression, downward expansion, three-band
equalization and bass boost further improve audio quality.
Built for the real world
• Easy installation and operation. Hybrids do not need to be adjusted
as you segue from caller to caller.
• Separately selectable single-ring auto-answer and auto-disconnect
function for assisted or unattended operation.
• Selectable auto mix-minus when mix-minus cannot otherwise be
created. Performance is best with a genuine mix-minus.
• Handy front panel controls and status indication, also available via
rear panel remote connector.
• Hybrid on/off controls and status.
• Send and caller level indication.
• Automatically accepts all worldwide AC power.
• Compliant with worldwide regulations, including FCC, CSA and CE.
All the right connections
• Inputs and outputs are balanced XLR and level on each is individually adjustable, ensuring the best audio mix.
• Send input accepts microphone and line levels.
• Auxiliary output provides either caller audio or a mix of caller and
local audio. Useful for recording and public address.
• An amplified speaker output, with rear panel 1/4" TRS connection
and front panel volume control, is provided for caller monitoring.
Three models to match your requirements
Comrex DH Series Hybrids are a great choice for talk shows, news feeds, production,
conferencing, Internet applications... any time you need great telephone sound. Select
the one that meets your needs.
Key differences among DH Series models
Digital Signal Processing
Digital signal processing hybrid
Acoustic echo cancellation
Selectable AGC and
caller ducking
Selectable AGC
and caller ducking
Adjustable compressor,
downward expander and
equalizer with bass boost
Audio processing
Selectable AGC and
caller ducking
Audio and Telephone Connections
Telephone line inputs
with Tel Set loop-thru
Balanced analog mic/line
send audio input
One with auto-conferencing
One with selectable
phantom mic power
Balanced analog on
hold audio input
AES/EBU digital
input and output
One each
1 watt into 8 Ω load
1 watt into 8 Ω load
2 watts into 8 Ω load
Monitor amplifier with front
panel volume control and
rear panel output
Control and Status
Front panel send and caller
audio level indication
Set-up and programming
Remote control and
status indication
Control of external recorder
Bicolor LED for each level
Bicolor LED for each level
Full LED VU meter
for each level
Front panel trim pots
and DIP switches under
access plate
Front panel trim pots
and DIP switches under
access plate
Front panel LCD and
multifunction buttons
with lockout
Logic interface
Logic interface
Logic and serial
Front panel buttons,
rear panel closures
and status output
Front panel selectable
Other Features
Alternate cue feed to caller
DH22 special features
• Auto-conference function sends common local audio (send) auto to
each caller mixed with the audio of the other caller—they hear the
other parties, but not themselves.
• Multiple external mix-minus setups are not required.
• Two digital hybrids balance each caller separately, avoiding the
problems inherent in “button mashing” two callers on one hybrid.
• Audio may be combined to a single output or as two separate
outputs to feed your console or mixer.
DH30 special features
• Both balanced analog and AES/EBU digital inputs and outputs.
• Acoustic echo cancellation improves hybrid performance and
eliminates feedback when used in studios and other venues with
open speakers and microphones.
• Remote controllable, password protected processing presets help
individualize processing for varied talent and programming.
Adjustable processing available to further improve audio quality are:
• Digital compressor and downward expansion.
• Three-band equalization with additional bass boost.
Additional controls available on front panel:
• Record function sends a start/stop signal to an external
recording device.
• Cue function switches audio signal sent to caller to “offline”
cue input.
• Comprehensive diagnostics suite to troubleshoot hybrid performance.
Need multiple hybrids
with multiline and call
screening capabilities?
The Comrex Studio Telephone Access
Center puts you in control with great
sound, ease of operation and scalable
configuration. Contact us for details.
DH Series
Hybrid performance
• Telephone transmit
• Frequency response: 250 Hz to 3.5 kHz, ±1 dB
• Signal-to-noise ratio: >56 dB
• Distortion: <0.2%
• Frequency response: 250 Hz to 3.5 kHz, ±1 dB
• Signal-to-noise ratio: >56 dB
• Distortion: <0.2%
• Send-to-caller separation: 55dB nominal
• Caller-to-send separation: 50 dB nominal
Audio processing
• Selectable automatic gain control (AGC)—Threshold
-50 dBm, works to achieve an equivalent average
caller level of -30 dBm from the telephone circuit
• Ducking control—adjustable from 0 to 18 dB in
6 dB increments
Audio connections
• Send input—XLR female: -55 dBu (mic level) or 0 dBu (line
level) nominal, adjustable, balanced, bridging, 20 k Ω impedance, DH30 provides selectable 12 VDC phantom power
• Caller output (one on DH20 and DH30, two on DH22)—
XLR male: 0 dBu nominal, adjustable, balanced,
50 Ω impedance
• Auxiliary output—XLR male: 0 dBu nominal, adjustable,
balanced, 50 Ω impedance
• Monitor output—1/4" TRS: 1 watt output on DH20
and DH22, 2 watt output on DH30 into 8Ω load
• Cue input (DH30 only)—XLR female: -55 dBu (mic level)
or 0 dBu (line level) nominal, adjustable, balanced, bridging,
20 k Ω impedance
• AES/EBU input/output (DH30 only)—XLR: 32, 44.1 and
48 kHz sample rate
Supplementary audio connections available on rear panel
DB-25 remote connector
• Send Input—0dBu nominal, adjustable, unbalanced,
20k Ω impedance
• Caller Output—0dBu nominal, adjustable, unbalanced,
50 Ω impedance
• Auxiliary Output—0dBu nominal, adjustable, unbalanced,
50 Ω impedance
Telco connections
• Telco line (one on DH20 and DH30, two on DH22)—RJ11
Plain old telephone service (POTS), analog extension from
PBX. A-Lead supervision provided
• Telco set provides loop-thru to standard telephone set or
other systems (one on DH20 and DH30, two on DH22)
Control connections
• Remote—DB-25
• Control inputs—activated with switch closure to ground
• Hybrid on/off, user selectable as momentary or latching
(two inputs, one for each hybrid, on DH22)
• Monitor audio mute
• Record start (DH30 only)
• Feed cue audio to caller (DH30 only)
• Send and caller audio mute (DH30 only)
• Activate up to three presets (DH30 only)
• Status outputs—Open collector rated at 30 VDC, 40 mA
• Hybrid on/off (two outputs, one for each hybrid, on DH22)
• Hybrid send/caller presence indication (two sets, one for
each hybrid on DH22)
• Record control (DH30 only)—DB-9: Provides start, stop and
enable commands to external recorder.
• Serial control (DH30 only)—DB-9: Connected to the serial
port of a PC or other RS-232 device, this port receives
commands to remotely control operation, request status
or download firmware upgrades.
Power and physical
• Auto adjusting power supply for 120/240 VAC 60/50 Hz
operation—20 watts
• Size: 19" W x 10.125" D x 1.75" H (48.26 cm x 25.7 cm
x 4.44 cm)—standard 1 RU EIA rack mounting
• DH20 and DH223 weight: 6.4 lbs (2.9 kg)
• DH30 weight: 6.7 lbs (3.04 kg)
• Operating environment: 32 to 100o F (0 to 38o C),
0 to 80% humidity
About Comrex
Comrex, an innovator in communications and telephony technologies for more than 40 years, provides reliable solutions to meet the
demands of live broadcast. Thousands of radio and TV stations trust
the quality of our products every day for news, sports and entertainment audio. The company is headquartered near Boston, Massachusetts, and Comrex products are offered and supported by a
worldwide network of dealers.
Comrex is registered trademarks of Comrex Corporation. Other trademarks
may be property of their respective owners. While every effort has been made
to assure accuracy, we are not responsible for errors or omissions.
Product descriptions and specifications are subject to improvement
or change without notice. Contents © 2007, Comrex Corporation.
All rights reserved.
Put Comrex On The Line.
Toll Free: 800-237-1776 • • e-mail: [email protected]
19 Pine Road, Devens, MA 01434 USA • Tel: +1-978-784-1776 • Fax: +1-978-784-1717
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