"Houston, we have problems."
I'm trying to simulate "Standby beep circuit".
(1) Timing control of PTT delay and starting beep sound
It is a little difficult to make good timing of start beep sound when I press PTT switch. Controlling delay time of PTT is not always easy as I expected.
I'm still adjusting it.
(2) Beep frequency is about 3KHz.
It is a little high. I'm adjusting it to be 2.5[kHz].