As I wanted to be able to use transmitters that didn't externalise the PTT, and also because I wanted to alert the final receivers that the transmission was a crossband one, I have added a beep that sounds before the delayed voice.  This can be heard by the receivers, and also serves to give the transmitter VOX something to trigger it quickly.

In addition, I added a flag to stop DAC output unless the delay VOX was triggered so that the quiescent input signal to the transmitter VOX would be as quiet as possible.

Code update soon.