3Com S21x installation manual Txd

Models: S21x

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V.24 Cable

V.24 Cable

V.24 DCE Cable The following table shows the DCE pinouts for the V.24 cable. These pins are assigned double functions in the V.24 cable:

Pin 15: Outputs TRANSMIT CLOCK if the port is configured for internal clocks. Otherwise it acts as a V.54 Loop 3 signal when connected to a modem.

Pin 22: Used as the Ring Indicator output if the port is configured to emulate a dial modem. For this to work properly, the RI/TM switch of the port must be set to RI. When the RI/TM switch is set to TM, this pin acts as an input, and the TM output from the attached modem (pin 25 on the modem) comes into the 6500 on this pin.

Pin

Function/Signal Name

 

 

1

Shield/Frame Ground

 

 

2

TXD

 

 

3

RXD

 

 

4

RTS

 

 

5

CTS

 

 

6

DSR

 

 

7

Signal Ground

 

 

8

DCD

 

 

14

DATA RESTRAINT

 

 

15

TRANSMIT CLOCK or V.54 Loop 3 *

 

 

16

STANDBY INDICATOR

 

 

17

RECEIVE CLOCK

 

 

18

EXTERNAL RECEIVE CLOCK

 

 

20

DTR

 

 

21

V.54 Loop 2

 

 

22

RI/TM *

 

 

24

EXTERNAL TRANSMIT CLOCK

 

 

25

TEST MODE

 

 

B-12

PathBuilder S21x Switch Cabling

Page 54
Image 54
3Com S21x installation manual Txd