0. can anybody tell me the principle behind this circuit? it used to
monitor the voltage level -about 8V (provided by Nang). i only know
that voltage level is depend on the zener diode and there is a
direct-coupled multistage amplifier. but i dont the mechanism of
1. what is the difference between Infrared, Ultrasonic and RF?
2. 27 MHz is VHF or HF?
3. if 1 tx/rx provides 4 command signals, can i use two tx/rx boards
(27 Mhz & 33 MHz) in order to get 8 command signals using the same