OSCILLATOR OUTPUT – A – Continuous 40 KHz. In this case the output will pulse LOW only once when the detector sees the signal. The signal will have to be removed before the output can again go LOW. If the signal is not removed the detector will in effect go blind and the output will remain HIGH.
OSCILLATOR OUTPUT – B – Pulsed 40 KHz. In this case the output will briefly LOW each time a 40 KHz pulse is received. The duration of the output pulse was shorter than the duration of the 40 kHz signal.
OSCILLATOR OUTPUT – C – Pulsed 40 KHz modulated at 833 Hz. The output from the detector produced 833 Hz pulses at a 7 Hz rate.
In this method, the 833 Hz pulses represent the data that the remote would be sending to the receiver.
Visit Here for more.