The Allen-Bradley 1771-IJC module, also known as the 1771-IJ module, is an encoder or counter module which can be used with Allen-Bradley processors that use the 1771 I/O structure. It keeps track of the input pulses from encoders, optimal beam counters, and switches. The 1771-IJC module can make decisions based on the total amount of these pulses and it can also share the amount with the processor for display or computations. The module has 2 outputs. The 1771-IJC module can be programmed through single-transfer programming when it is used in a local I/O chassis and also through block transfer programming which can be used at any time. The peak input pulse frequency which the 1771-IJC module can detect is 50 kilohertz. The module requires an external 5 Volts DC power supply that is capable of delivering 140 milliamps of current with less than 50 millivolts of ripple peak to peak. The power is supplied to the module through the chassis backplane.

The 1771-IJC module comes with two 12-terminal gold-plated field-wiring arms. The devices inputting signals to the 1771-IJC module should be capable of delivering 16 milliamps of current. Voltages above 2.4 Volts DC are considered to be logic “1” (true) and voltages below 0.6 Volts DC are considered to be logic “0” (false). The input devices should be within 40 cable feet of the module. For signals below 20 kilohertz, the Belden 8761 cable can be used while the Belden 9182 cable can be used for signal frequencies going up to 50 kilohertz. The 1771-IJC module can be installed in any 1771 I/O chassis. The power to the chassis backplane and wiring arm should be removed from the module before it is inserted or removed.