Devices {telephone}| can receive and transmit human speech sounds. After two telephones are on a circuit, direct current from telephone-central-office batteries flows through circuit.
microphone
Microphones {mouthpiece, telephone} can be a round box filled with powdered carbon, covered by a flexible diaphragm. Sound compresses diaphragm and carbon, to change carbon electrical resistance and make waves in electric direct current.
speaker
Speakers {earphone, telephone} can have an electromagnet and metal diaphragm, which current waves vibrate.
wire
Telephones use three wires: one to electrical ground, one for telephone line, and one for ringing line.
dialing
Dialing telephones activates relay switches that select correct wire pair to connect to dialing telephone. Dialing then activates ringing circuit. When other telephone answers, telephone-line circuit is complete. If other telephone line is already in use, the dialing process sends a busy signal.
Practical Affairs>Machine>Kinds>Electronic>Sound>Telephone
7-Machine-Kinds-Electronic-Sound-Telephone
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Date Modified: 2022.0224