David E A Wilson <david@cs.uow.edu.au> (05/03/91)
acd4!mjt@uunet.uu.net (Mark Teegarden) writes: > P.S. Could someone please post a wiring diagram for an RS232 Y-cable > that could be used to attach the serial line of a second PC to monitor > the serial transmissions of the first one that is running the Prodigy > Software without wreaking havoc on the communication to and from the > modem? Can this be done inexpensively? HOST End MODEM End DB-25F DB-25M 4 (RTS) >--------------------------------------> 4 (RTS) 5 (CTS) <--------------------------------------< 5 (CTS) 20(DTR) >--------------------------------------> 20(DTR) 6 (DSR) <--------------------------------------< 6 (DSR) 8 (DCD) <--------------------------------------< 8 (DCD) 7 (GND) --------+------------------------------- 7 (GND) 2 (TxD) >---------------+----------------------> 2 (TxD) 3 (RxD) <-----------------------+--------------< 3 (RxD) | | | | |a |b | \ | \ | \ SPDT switch a=monitor TxD | \ b=monitor RxD | | | | MONITOR DB-25 7 (GND) 3 (RxD) connector to suit tty/pc This should work if plugged into your modem and the cable from your PC to the modem plugged into the DB-25F. If the monitoring computer does not use a DB-25 then the pin numbers at the bottom of the diagram will change. The monitoring pc/tty may also require loopback connections to enable its receiver: typically this would be 4-5 & 20-6-8 joined in the monitor DB-25. David Wilson Dept Comp Sci, Uni of Wollongong david@cs.uow.edu.au