Phone Hold With Music
current to pass through to prevent the phone company from disconnecting the call. The resistor R2 and LED provide a visual indication that you have someone on hold ( this is optional )
The capacitor C1 and the transformer provide the interface to a radio or CD player headphone jack. Before you hook up the project to the phone line you must determine the polarity of the line. Place a voltmeter across the red and green wires of the telephone line, there should be about 48 volts
DC positive when the black lead of your meter is connected to the green phone wire. If it is negative 48 volts then reverse the wires.
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