[Al Skierkiewicz]

Once you throw a radio link into the mix you suddenly complicate things. A simple control cable with 12 wires is the simplest, no need for encode or decode. You can use logic blocks to decode 1 of 10 switch inputs to BCD, transmit that via 6 wires and then decode back to decimal at the relay box. This requires a logic power supply at each end. You could use a voltage encoded generator (i.e. a circuit that generates 10 different voltages) send it over a pair of wires and decode with a window comparator back to one of ten at the relay box. Or you can use telco tone encoding and decoding using DTMF(Dual Tone Multi Frequency). You could use that to modulate an ultrasonic transducer for hand held remote operation. Or there are a number of chipsets for remote Infrared communication available, just search the Internet for part numbers. There should be a number of books at the library on remote control you could consult. If you need to activate more than one relay at a time you need to have control over the on and off charachteristics which may require electronic latches. There are relays that latch but they are expensive. For those you pulse them with voltage to change states. I know this doesn't help much but what you ask for is a rather interesting electronic problem for designers and there are a variety of solutions based on what your needs are..