Use of a Null Modem Cable

Owned by Jack Degrano
Last updated: Apr 26, 2024 by Corey Boyles
1 min read

When using an ACR controller card in an ACH chassis or with an Acroloop Breakout box, the serial connections COM1 and COM2 are made with a DB9 male connector. This connector is intended to be used with a 3 wire "NULL MODEM" cable to a DB9 male connector supplied on the computer running the AcroView for Windows (Serial) program.

This Cable crosses the Transmit and Receive inputs of the COM port and supplies a ground connection on each end. Pin2 is connected to Pin3 on the opposite end and Pin5 is connected to Pin5.

 

NOTE: If a purchased "NULL MODEM" or "LAPLINK" cable is used, Pin1 can not be grounded or this cable can not be used. The ACR controller card uses Pin1 for multiplexing controller cards and grounding Pin1 disables the card. (See Typical Connection Manual for controller card for wiring details.)