It is the job of the IR receiver to decode the signals coming from the transmitter. A PIN diode IR sensor receives and demodulates the signal. All major functions are processed in a custom integrated circuit (IC). It has several modes of operation such as creating momentary or latching outputs. It could also activate the outputs in “rotary” fashion.
In our case, we are only interested to activate any of eight outputs for only as long as the corresponding button of the transmitter is pressed. The outputs are of the open collector type. In other words, an active output can sink up to 50 mA from an external voltage source of up to 50 VDC.
For all practical purposes, we can think of the receiver having eight switches which are normally open and close, one by one, as a button of the transmitter is pressed. Refer to the next section that explains how the outputs are used.
The power source for this board can be a center-tapped 24 VAC voltage or a 12 VDC voltage. An on-board regulator generates 5 VDC for the internal logic circuitry.