User`s guide

A Dsub-25 female connector viewed from the front
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\ 13 12 11 10 09 08 07 06 05 04 03 02 01 /
\ 25 24 23 22 21 20 19 18 17 16 15 14 /
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If you can find a couple old-style Dsub-25 plug casings, the sockets can be
mounted and the casings can be glue-gunned together to make a nice compact unit.
For Apple2-PC (or Mac, etc.) transfers, you plug the modem cable from the
Apple II into one side of the NULL modem and the modem cable from the PC into
the other side. If the PC has a 9-pin serial port connector, use a 9-to- 25
adapter cable to connect to the NULL modem. Similarly,for Mac users, if the Mac
cable has a special connector, use a converter to a male Dsub-25M connector for
plugging into the NULL modem.
Dedicated IIgs NULL modem cable
The usual IIgs NULL modem cable consists of a High-Speed IIgs modem cable
connected to a NULL modem adapter which connects to a modem cable coming from
the PC. If you want to 'roll you own' single piece IIgs --> PC cable for NULL
modem connections, here is the pinout info:
IIgs PC Female Dsub
Mini-Din 8 Dsub-25F or Dsub-9F Dsub Signal
3 3 2 RXD
5 2 3 TXD
4,8 7 5 GND
2 4 7 RTS
1 5,6,8 1,6,8 CTS, DSR, DCD
7 20 4 DTR
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007- What is the maximum length for a computer-to-
computer NULL modem hardware-handshaking connection?
Most texts agree that around 50 feet is the 'safe' maximum length.
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008- What are the connections for a standard modem cable?
The standard modem cable which can support hardware handshaking connects
eight lines between two male Dsub25 connectors: