When I'm out working in the shop, I often find myself wanting to call up to the house-"When do you want to eat lunch?"-but I don't want to dig the cell phone out of my pocket with greasy hands and I've never been able to convince my girlfriend that walkie-talkies As it turns out, the "talking" part is actually quite simple. Putting 20-30mA through the circuit will allow the handsets to work normally; pressure from the sound of my voice on the carbon granule microphone modulates the current, which in turn causes the speaker on the other end to reproduce the sound. If you don't want to get too far into electronics, you may want to stop here-you can build this circuit with just a battery and a resistor.
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