At 12/7/2006 10:54 AM, you wrote: >It normally takes two 555 timer chips for a basic cor function. One >timer is set up to add tx tail/hang time and the other to ensure >the exceeded tx time-out time function shuts the transmitter down. >A lot of people get cheap and replace the tail timer with a resistor >cap method, which is not nearly as cool as a well done 555 circuit.
How about using good ol' op amps? I like that approach because almost the entire basic controller can be implemented using a single chip: 2 op amps for hang time & TOT, 2 left for audio processing. Add a JFET for squelch audio gating & you're done. The TLV2374 features rail-to-rail operation so it makes a good comparitor, yet also has good audio distortion characteristics so long as the output stays at least 1.4 V away from the positive supply rail. It's a good choice for such multi-purpose use. Bob NO6B
