Product Description
The 770.91.20 is a 4 Channel Drive Interface Module. It initially was made by Reliance Electric but may have been also mass-produced by ABB and Baldor Reliance at some point. This module is no longer supported by these companies and may be difficult to find. AX Control does attempt to keep the 770.91.20 in stock.
The faceplate on the 770.91.20 has several features. There are four female 9-pin RS-232 connection ports that are labeled Port 1 through Port 4. There is a small fault code LED display that is 7-segment. Its function is to display a code when it detects an error within the module. There is also a small green LED directly below it that is labeled OK. This module has the ability to be plugged into a card rack assembly and can be mounted to the rack using the two brackets located on the top and bottom of the faceplate. These brackets can also be used to gently insert or remove the module from its card slots on the rack.
When the user opens the case on the 770.91.20, they can gain access to the internal circuitry of the module. There are two factory-drilled holes at each of the four corners of the circuit board. These holes can be used to mount the board into its protective case. There are many capacitors and relays on the board along with 49 integrated circuits, 3 EPROMS, 16 transistors, 10 resistor networks, and 16 square relays. There are also the RS-232 port connections.
When handling the internal circuitry of this module, be sure to use antistatic procedures