> Here's how we've designed our controllers' COR, CTCSS, and > logic inputs for many years: Feed the COR signal to the top > of a voltage divider. The upper resistor is 10K and the lower > is 4.7K. Feed the junction of the divider to the base of an > NPN such as a 2N3904, 2N2222, etc. You'll have a 3:1 voltage > divider that in essence multiplies the transistor's > base-emitter drop by three, so the input threshold will be > ~2V instead of ~0.7V. And, you'll have 10K and an NPN to > buffer the outside world from whatever logic IC you're using > for your input port.
Seems that sick minds think alike, Bob :-)
