Black Box 34336 User Manual

Appendix A:  DB25 Pin Assignments

1

AA

Frame ground—not connected

2

BA

Transmit data (TD)

TD

DTE

3

BB

Receive data (RD)

RD

Modem

4

CA

Request to send (RTS)

RS

DTE

5

CB

Clear to send (CTS)

CS

Modem

6

CC

Data set (modem) ready (DSR)

MR

Modem

7

AB

Signal Ground (SG)

Ground

8

CF

Carrier Detect (CD)

CD

Modem

9

+P

Testing voltage, +10V

Modem

10

-P

Testing Voltage - 10V

Modem

15

DB

Transmit Clock (TC)

Modem

17

DD

Receive Clock (RC)

Modem

18

CN

Analog loopback (ALB) control

1

DTE

20

CD

Data terminal ready (DTR)

TR

DTE

21

CN

Remote digital loopback (RDL) control

1

DTE

22

CE

Ring Indicator (RI)

R

Modem

23

CH

Speed Select (CH/CI)

2

DTE

24

DA

External transmist clock

DTE

25

CN

Test mode indicator (TM)

3

TM

Modem

+voltage activates indicated loopback test (only if ALB-DTE controled
or RDL-DTE controled option is enabled); -voltage disables test.

+voltage, 14,400 bps; -voltage, 2400 bps.

Alternatively, pin 25 may be used for analog loopback (ALB) control.
See Appendix D.