The circuit is run by 555 timer IC for its PTT sequence that is 4 seconds "on" and 4 seconds "off". Transmission is about 50% duty cycle that minimize the transmitter heat. Tone IC is any thing that generates sound, I got mine from a magnetic door open sensor which I bought from Japanese Store in Festival Mall. The prototype when connected to a portable transceiver is ready to go on air. ---73 de hevir
