Thread: Codar AT5 TX
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Old 20th Feb 2021, 11:11 pm   #28
Keith
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Default Re: Codar AT5 TX

Old telephones used a carbon microphone (variable resistance). You'll need to supply a couple of volts to pass some current through it. If you pass this through the low impedance primary of a step-up transformer you'll get plenty of audio on the secondary.
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