Alright, here's my problem. I have a radio at work, a Radius CP220 by Motorola. It's one of those commercial looking ones, VHF I believe. Either way, it has a connection for headphones. The problem I'm having is I'll be listening to my CD player or MP3 player loudly and won't hear the radio when my boss is yelling at me. So what I would like is a relatively simple circuit that would cut the CD player and funnel the radio through to the headphones when the radio is giving sound (I'm pretty sure it's at ground when there is no sound), and go back to the CD player when it finishes. I'm thinking this would involve a comparator or two and a transistor/relay, but I'm probably wrong. Can someone point me in the right direction?
so what you want is a swtich that will (once it detects a signal from the radio) change to the radio and then back to the CD when your boxx has finished talking. My feeling is for you to go with a type of logic gate system. Split the signal between the radio and the logic and then once you start to recieve a signal from the radio the logic cuts the CD and thus allows you to hear your boss. You should need an XOR gate in some sort of circuit. i cant think of how but that would do it. Edit:: hopfully ill spark a few ppl with this one. logic gates need a certain level of voltage to switch. If the radio signal is above that (using a pre amp) then that would switch the XOR gate AND allow the variations in the voltage to pass through to the speakers as long as it did not go above the celling limit (distortion). Once the boss stops speaking the XOR gate switches again allowing for the CD signal to come through.
The "hard" part in this will be filtering the signal from the radio and converting it to a TTL signal, after that you just have to make a delay funktion that switches to the radio immediately, a relay is easiest, and then back to the CD after a set time.
