DEC VT420 Service Manual page 75

6 DSR2
J2 DEC-423 Comm2/Printer Port Connector
Pin 1 HPTRDTR
2 HPTRTXD
3 GND
4 PTRCOM
5 PTRRXD
6 PTRDSR
J3 RS-232 Comm1 Port Connector
Pin 1 GND
2 HTXD1
3 RXD1
4 HRTS
5 CTS
6 DSR1
7 SIG GND
8 HCD
9 Not used
10 Not used
11 Not used
12 SPDIND
13 Not used
14 Not used
15 Not used
16 Not used
17 Not used
18 Not used
19 Not used
20 HDTR1
21 Not used
22 Not used
23 HSPDSEL
24 Not used
25 Not used
J4 Keyboard Port Connector
1 HKBTXD
2 GND
3 +12 V
4 KBRXD
Physical/Functional Diagrams 67
Data set ready
Data terminal ready
Transmitted data
Transmit ground
Receive ground
Received data
Data set ready
Ground
Transmitted data
Received data
Request to send
Clear to send
Data set ready
Signal ground
Carrier detect
Speed indicator
Data terminal ready
Speed select
Transmitted data
Ground
Received data