The IR2 is a two piece Infrared transmitter/receiver pair that works together to provide a read-only toggle input control for the HAL system. The IR2S sends an infrared beam of light and the IR2R receives the beam. When the IR2R (receiver) senses infrared, the toggle is checked (wall open). The toggle is unchecked when the IR2R doesn't sense the beam (wall closed).
Both the HAL2 and DR4 provide ports for IR Remotes, which the IR2 connects to via a single CAT 5e cable. The following picture shows an IR2R/IR2S pair correctly wired to a CAT 5e cable and also the elements of the remotes.
When wired correctly, green indicators on the IR2R and IR2S are always lit. Only when the door is open and the IR2R is receiving infrared from the sender does the IR2R’s amber indicator light. The HAL does not check the IR2 wiring for errors. The IR2R’s green indicator flashes when the output is short-circuited. The amber indicator flashes when the signal is marginal, as for a dirty sensor, or if it’s too far away. The IR2 will operate with up to 5 feet (1.5 meters) between sensors.
note: Distinguishing the IR2R from the IR2S: Both the send and receive IR parts have brown and blue wires, but the receiver also has a black wire.