InfraRed Remote Control Tester

This small InfraRed Remote Control Tester circuit is used for checking the operation of an infrared remote control unit. The circuit is based on the idea of connecting a piezo buzzer directly to an IR receiver IC.Operation of the remote control is indicated by the buzzer making a chattering noise. The circuit is very sensitive and has a range of several metres.
The TSOP1738 integrated IR receiver accepts, amplifies and demodulates the IR signal from the remote control, producing an output with a frequency of around 700 Hz. The piezo buzzer is connected to its output, rendering the signal audible. All the other components are simply concerned with producing a stable 5 V power supply from the 9 V PP3-(6F22) type battery.
Instead of the TSOP1738 similar devices from other manufacturers can be used, and of course carrier frequencies other than 38 kHz can be used. The circuit still works if there is a mismatch between the nominal carrier frequencies of the transmitter and receiver IC, but range is reduced. It is still, however, adequate for determining whether a remote control is producing an IR signal or not.
Ref:http://electroschematics.com