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What I was referring to was the capability of within the same frequency band ( on the input) to control the repeater ( say 2 meters) in the same fashion one would open the autopatch and get weather, temps, and voice readout of the power of the repeater using the same 2 meters to accomplish this.
Not all repeaters use 440 or 222 for links to control the transmitter, the input on the two meters is used for this. I have seen a repeater trustee control the repeater just using his 2 meter handheld.
For none hams, repeaters are duplex. The functions for controlling the autopatch and the coding is done through the input and the output is squelched so that no one can pick up the tones.
Using this reasoning, one could come up with a basic DTMF signaling system for controlling a transmitter in the same band on the same frequency is the STL link. ie: Simplex
Where as 2 meters is duplex, We could go SIMPLEX on the STL it is feasible to put a sensing circuit with a DTMF decoder in the STL receive on the part 15 transmitter using the same STL feed frequency as the audio is on.
It doesn’t have to be used on the the FM broadcast band as a STL link, any frequency thats legal to use would be fair game. But instead of using two separate STL frequencies to do the audio link and the telemetry, one could do both functions on one STL link …using techniques as the ham ops use.
