Appendix I - RS232C Interface Specifications. Black Box MD1641A, MD1640A

APPENDIX I: RS232C Interface Specifications

Appendix I - RS232C Interface Specifications

The Series II Modem's RS232C interface circuits have been designed to meet the electrical specifications given in EIA (Electronic Industries

Association) RS232C standards. All signals generated by the modem are approximately 10 volts when measured across a load of 3000 ohms or greater. The receiving circuits of the modem will accept signals in the

3 to 25 volt range. The voltage thresholds are:

Negative = voltage more negative than –3 volts with respect to signal ground

Positive = voltage more positive than +3 volts with respect to signal ground

SIGNAL INFORMATION: NEGATIVE POSITIVE

Binary State

Signal Condition

Control and Timing Function

One

Mark

Off

The input impedances of all modem circuits which accept signals from the data processing terminal or CPU equipment have DC resistances of

4.7K. For more specific details, consult the EIA RS232C standard itself.

The following chart lists the EIA RS232C interface pins and circuits present on the Series II Modem's RS232C Interface connector. All other pins are unused.

Pin

No.

Abbrev.

EIA CCITT Signal Function

Circuit Circuit Source

Zero

Space

On

6

7

8

9**

12

1

2

3

4

5

PG

SD

RD

RTS

CTS

DSR

SG

CD

+v

HS

--

BA

BB

CA

CB

15*** TC

17*** RC

20

DB

DD

TR**** CD

CC

AB

CF

+v

--

--

--

107

102

109

101

103

104

105

106

114

115

108/2

--

DTE

DCE

DTE

DCE

DCE

--

DCE

DCE

DCE

DCE

DCE

DTE

Protective Ground

Transmitted Data

Received Data

Request to Send

Clear to Send

Data Set Ready

Signal Ground

Carrier Detect

Test Voltage

High Speed

Transmit Clock

Receive Clock

Terminal Ready

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SERIES II INTELLIGENT DATA/FAX MODEMS

22

24

25

RI

XTC

OOS

CE

DA

CN

125

113

142

DCE

DTE

DTE

** Pin 9 need not be present in your RS232C cable

*** Pins 15 and 17 are necessary only for synchronous operation

**** Also known as DTR (Data Terminal Ready)

Ring Indicator

External Transmit Clock

Terminal Busy

The computer or terminal should be supplied with a cable terminated with a Cinch DB25P (or equivalent) connector mounted in a Cinch

DB51226-1 (or equivalent) hood assembly as specified by the EIA

RS232C standard.

Functional Description of RS232C Signals:

Transmitted Data - Pin 2, SD (BA)

Direction: to modem

Signals on this circuit are generated by the customer's terminal and transferred to the transmitter of the Series II Modem. A positive signal is a space (binary 0) and a negative signal is a mark (binary 1). The transmitting terminal should hold this line in the marking state when no data is being transmitted, including intervals between characters or words. The TRANSMIT (XMT) LED indicates the status of this circuit.

Received Data - Pin 3, RD (BB)

Direction: from modem

The lead is the data output of the modem. Data signals received from the remote modem are presented on this line. When no carrier signal is being received (pin 8 negative), this line will be forced into a marking condition. The RECEIVE (RCV) LED indicates the status of this signal.

Request To Send - Pin 4, RTS (CA)

Direction: to modem

The RTS signal indicates to the modem that the computer or terminal has data that it wants to transmit.

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APPENDIX I: RS232C Interface Specifications

Clear To Send - Pin 5, CTS (CB)

Direction: from modem

The CTS line indicates to the terminal that the Series II Modem will transmit any data present on the Transmit Data line (pin 2).

Data Set Ready - Pin 6, DSR (CC)

Direction: from modem

DSR On indicates that the Series II Modem is in the data mode and is connected to the communications channel. This signal will be on during analog-loop-test mode.

Signal Ground - Pin 7, SG (AB)

The SG lead is connected to signal ground of the modem. It establishes the common ground reference for all other interface signals.

Data Carrier Detect - Pin 8, CD (CF)

Direction: from modem

DCD On (positive voltage) indicates that data carrier has been received from the other modem. This circuit will not normally turn on in the presence of message circuit noise or out-of-band signals. There is a one second delay between when the carrier tone has been detected and when the CD circuit is turned on.

This signal goes off if received data carrier falls below the receiver threshold for more than 37 mSec. When CD is off, the Received Data circuit (pin 3) is held to the marking state.

Test Voltage - Pin 9, XV

Direction: from modem

The XV lead has 330 ohms of resistance to +12 volts DC. This lead may be used to strap other signals high. For example, if the terminal does not supply a DTR (Data Terminal Ready) signal, Pin 9 may be jumpered to Pin 20 (DTR) on the RS232 connector or in the cable to force DTR on.

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SERIES II INTELLIGENT DATA/FAX MODEMS

Transmit Clock - Pin 15, TC (DB)

Direction: from modem

The TC signal is provided only when the Series II Modem is used in the synchronous mode. The clock is a square wave and is used to provide the computer or terminal with timing information for its Transmit Data circuit (pin 2). This clock will be provided on the interface at all times when the modem is in Synchronous mode.

The first signal element of the Transmitted Data signal should be presented by the terminal on the first positive (Off to On) transition of TC which occurs after the CTS circuit on pin 5 has turned on. The transmitted data is sampled by the modem on negative transition of TC.

Receive Clock - Pin 17, RC (DD)

Direction: from modem

The RC signal has the same characteristic of Transmit Clock, with the exception that it is used to provide the computer or terminal with timing information for its Receive Data (pin 3) circuit. The negative transition (On to Off) of RC indicates the center of each signal element on the Received Data circuit.

Data Terminal Ready - Pin 20, TR or DTR (CD)

Direction: to modem

This signal (TR or DTR) provides a means for the terminal or computer to control the modem's connection to the communications channel. A high DTR signal is required by the modem to be able to communicate.

Turning DTR off for more than 50 mSec will force the modem to disconnect.

The most common use of DTR is in automatic answer applications. A high DTR signal is required by the modem to answer a call. A frequently used method is to have the computer turn on DTR in response to RI

(Ring Indicator), which allows the modem to answer. Later, DTR is

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APPENDIX I: RS232C Interface Specifications turned off at the conclusion of the log off procedure, which forces the modem to disconnect, enabling it to receive another call. In non auto answer applications it is advisable to leave DTR on using the modem's

DIP-switch option. This is the standard factory setting. An alternative is to provide a constant high DTR from the terminal or computer. The

Data Terminal Ready (DTR) LED indicates the status of this signal.

Ring Indicator - Pin 22, RI (CE)

Direction: from modem

This signal will remain on for the duration of the ringing signal. When a ring signal is received by the modem, the modem will automatically answer after the first ring. The modem will answer after a specified number of rings which can be programmed in AT Command mode, but if none is specified, the modem will answer after the first ring.

External Transmit Clock - Pin 24, XTC

Direction: to modem

Supplies the same function as transmit clock on Pin 15.

Terminal Busy (Out of Service) - Pin 25, OOS

Direction: to modem

The Terminal Busy (OOS) circuit is not defined in the RS232C standard, but is used by us and most manufacturers to make the phone lines busy to incoming phone calls. Pin 25 is not normally connected to the RS232C interface when shipped from the factory; it can be ordered connected as an option. If pin 25 is connected and is brought high, the modem will be placed Off Hook, and busy to incoming calls.

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SERIES II INTELLIGENT DATA/FAX MODEMS

Appendix J - Regulatory Information

FCC and IC EMI/RFI Statements

When correctly installed and maintained, the modem will present no hazard to the user. When correctly installed the modem will be connected to the PSTN or a PW and to a Data Terminal Equipment

(DTE), whose modem connections comply with ITU recommendation

V28. The DTE connections are therefore taken to be safe voltages (less than ± 30 volts).

This equipment generates, uses, and can radiate radio frequency energy and if not installed and used properly, that is, in strict accordance with the manufacturer’s instructions, may cause interference to radio communication. It has been tested and found to comply with the limits for a Class A computing device in accordance with the specifications in

Subpart J of Part 15 of FCC rules, which are designed to provide reasonable protection against such interference when the equipment is operated in a commercial environment. Operation of this equipment in a residential area is likely to cause interference, in which case the user at his own expense will be required to take whatever measures may be necessary to correct the interference.

Changes or modifications not expressly approved by the party responsible for compliance could void the user’s authority to operate the equipment.

This digital apparatus does not exceed the Class A limits for radio noise emission from digital apparatus set out in the Radio Interference Regulation of Industry

Canada.

Le présent appareil numérique n’émet pas de bruits radioélectriques dépassant les limites applicables aux appareils numériques de la classe A prescrites dans le

Règlement sur le brouillage radioélectrique publié par Industrie Canada.

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