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Appendix
Appendix F

RS-232C Interface Specifications

The MT2834MR6’s serial interface circuits have been designed to meet the electrical specifications in EIA
(Electronic Industries Association) Recommended Standard 232, Revision C (RS-232C). 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 accepts signals in the 3 to 25 volt range. The voltage thresholds are
defined as follows:
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 One Zero
Signal Condition Mark Space
Control and Timing Function Off On
The input impedances of all modem circuits that accept signals from the data processing terminal or CPU
equipment are 4.7KW. For more specific details, consult the EIA RS-232C standard. The following chart lists
the EIA RS-232C interface pins and circuits present on the MT2834MR6’s RS-232C serial interface
connector. All other pins are unused.
Pin Multi-Tech EIA Signal
Assignment Designation Circuit Source* Circuit Function
1 PG — — Protective Ground
2 TD BA DTE Transmitted Data
3 RD BB DCE Received Data
4 RTS CA DTE Request to Send
5 CTS CB DCE Clear to Send
6 DSR CC DC E Data Set Ready
7 SG AB — Signal Ground
8 CD CF DCE Data Carrier Detector
9 +V +V DCE Test Voltage
12 HS - - DCE High Speed
15 TC DB DCE Transmit Clock
17 RC DD DCE Receive Clock
20 TR CD DTE Data Terminal Ready
22 RI CE DCE Ring Indicator
24 XTC DA DTE External Transmit Clock
25 O OS CN DTE Terminal Busy
* DTE = Data Terminal Equipment (terminal or computer)
DCE = Data Communications Equipment (the modem)
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 RS-232C
standard.