The Allen-Bradley 1785-O5G PLC 5 Coprocessor Module serves as a backup module. This module comes with an RS-232-C Port and the backplane current of this module is 2.7 A at 5V DC. This module has a maximum of 3072 analog I/O. The I/O Scan Times Per Rack of this module are 10 ms at 57.6 kbits/s, 7 ms at 115.2 kbits/s, and 3 ms at 230.4 mbits/s. The Allen-Bradley 1785-O5G is intended for use in a Pollution Level Industry Environment 2, in excessive Category II applications (as defined in the publication of IEC 60664-1). Please remember that this power supply can operate at an altitude of up to 6562 feet without derating. If you connect or disconnect the cable and the terminal block and if you install or remove the 1785-O5G when the power is on, an electrical arc may occur. This can cause injury, damage, or even an explosion in hazardous locations. Make sure the power is removed and that the area is not hazardous before continuing. The operating temperature is 0 to 60 °C (32 to 140 °F), the storage temperature is -40 to 85 °C (-40 to 185 °F), and the relative humidity is 5 to 95% without condensation. The Allen-Bradley 1785-O5G has an operating shock of 30g (3 pulses, 11 ms) and a nonoperating shock 50g (3 pulses, 11 ms). This module must be installed in an enclosure with at least IP54-level protection for operation in Zone 2 environments.

The 1785-KA3 PLC-2 Family Communication Adapter Module by Allen Bradley is a communication adapter installed on any slot (except the furthest left) of the 1771 I/O chassis, which links the PLC-2 family processors to a Data Highway Plus (DH+) Network. The 1785-KA3 draws 1.2 A backplane current at 5 Volts DC. It has an interface port for connection to the PLC-2 Programmable Controller using the Data Highway Plus Processor cable and a Data Highway Plus drop-line, and for connection to the 1784-T50 Industrial Workstation using the Program Panel Interconnect Cable. The 1785-KA3 has 3 sets of switches: the Data Highway Plus baud rate switch assembly, the write options switch assembly and the node address group switch. These switches determine the mode of connection with other nodes on the network. This unit supports most PLC-2 family processors, and the module is keyed to the backplane by connecting the band between pins 4 and 6, 22 and 24 of the top connector. Its temperature range is between 0 and 60 degrees Celsius (32 to 140 degrees Fahrenheit) at 5% to 95% non-condensing relative humidity; its storage temperature is between -40 to 85 degrees Celsius (-40 to 185 degrees Fahrenheit).