Stan had brought up the issue of these cheap transmitters operating continuously and thus not allowing for the possibility of multiple systems in the same area. I've been thinking about that issue.
One approach is to bring in the input signal, condition it, and feed it to a microprocessor. The uP would then do a simple encoding of the status and send out a brief (100-200 millisecond) encoded state for the input. With four bits, I could transmit up to 8 states using three of the bits, (probably 7 as 000 would not be recognized by the transmitter). The 4th bit indicating the state of the input, active or inactive. The transmissions would only take place once during initialization to set the initial states of each input, and then only upon a change in the input state. This would consume very low bandwidth and allow for many of these systems to coexist if desired.
The receiver could then send this simple encoded signal to another uP for the decode. That uP would convert the signal into the desired action, for a backup light for instance, it would simply toggle it on by command until it received an "off" indication. If you were triggering a coupler, it would trigger it for perhaps 1/4 second, similar to what the TMCC or DCS system handles them.
I need a motherboard anyway for signal conditioning on the inputs and of course the DC power for the radios. For the receiver, I'll also have signal drivers of some sort, depending on what capabilities we envision this link having.
I'm also thinking of routing serial data to the uP in the case of TMCC or Legacy and being able to trigger events based on the serial data stream.
