--- In [email protected], "Bruce Morgan" <[EMAIL PROTECTED]> wrote: > I have a question about logic circuits. I have a Yaesu FT 1500 that has the data port on the back and I want to use the 1500 as a temporary receiver in my repeater while the acutal receiver is out for repairs. Here is my problem, the data output port has a COS pin out (Carrier=5 volts, none = 0 volts) My contoller port says, Receive COS (pull this input low when receiving). > > So I need to turn my positive logic signal to a negative logic signal. I found this circuit to do the the opposite of what I need please explain how you came to the conclusion that the circuit would do the opposite of what you need. This circuit is about as simple as you will ever encounter. A NPN transistor in a common emitter configuration. The resistor on the base limits current in the base-emitter junction from destroying it. A positive voltage from emitter to base higher than about .65-.7 volts will cause the transistor to saturate and the collector to emitter junction will look like a near short. The +V will drop across the load resistor on the collector and the collector will look like ground or 0 volts. When 0 volts is applied to the input or COS the resistor on the base, the emitter to collector junction looks like an open circuit and the voltage at the collector is what ever +V is. A simple inverter circuit.
( http://www.repeater-builder.com/pix/cosswitch.gif ) Can I and if so how can I modify this to produce the positive logic with no signal and negative logic when a carrier is present. > > Or is my line of thinking completely out of line? > Thank you. Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
