multichannel rf transmitter and receiver

Anyone knows where can i get the circuit diagrams of multichannel radio frequency transmitter and receiver circuit diagram??Thank you very much 4 ur help.

well from the circuits from the radio controlled cars i played with there were chips one on transmitter labeller TX and one on the reciever called RX and thats all that was written o it. from the schematic i realized that the TX had a 6 bits paralel input and a serial output, and the Rx had a serial input and a 6 bit paralel output. i couldnt find any info about these ics, because there was nothink elese writen on htem.
but here are some ics that do that
HT12A transmitter, and HT12D receiver, but you need a radio or ir circuit as well

Here is a website you might find useful. The author seems to be pretty experienced in the area of transmitters and receivers and he has a forum you may want to post your message at. **broken link removed**