The AB 1771-DXPS is a member of the 1771 control coprocessor module series. It handles a 7-bit reception even-parity which is an expander module. It provides an ASCII display and additional ports. This module has a COMM 2 and a COMM 3 port and these are 25-pin, optically-isolated, serial communication ports that are defined by EIA RS-232C, -423, and -485 standards as ports that can support communication. The 1771-DXPS has a spring-loaded key switch. The control processor can reset positions that are used for reinitializing without cycling power. The control processor of this module can provide information which is displayed in an ASCII display. The LEDs provide information about the COMM 2 and COMM 3 ports’ status. Upon detecting a fault in the module, a fault relay will contact the switch and this will relay a 500 mA signal at 30V AC/DC which is resistive. To install the expander module, you need an ESD grounding wrist strap, a power supply, chassis keying bands, and a chassis that is properly grounded.

The 1771-DXPS module is very sensitive to ESD or Electrostatic Discharge. Semiconductors or integrated circuits can be damaged by an ESD.