Electrical Communication - Passive or Generator-Type Telephone Transmitters

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Home Electroacoustic Devices Passive or Generator-Type Telephone Transmitters
See also: Active or Modifier-Type Telephone Transmitters

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Passive or Generator-Type Telephone Transmitters In these transmitters (or microphones) all the electric power output must come from the acoustic power in the sound waves. The passive transmitters are, therefore, essentially electric generators with internal impedance and an open-circuit output voltage that is a replica of the sound waves. Passive or generator-type transmitters can be grouped in two classes: the magnetic microphone, defined¹ as "a microphone the electric output of which is generated by the relative motion of a magnetic field and a coil or conductor located within the magnetic field," and the crystal microphone, which is a microphone that operates by virtue of the piezoelectric effect. These devices will be considered in detail later in this chapter. The electric power output of a passive or generator-type transmitter is very low, because the electric power output comes entirely from the acoustic power of about 10 microwatts actuating the transmitter, and because the efficiency of transforming from acoustic to electric power is a few per cent.
Home Electroacoustic Devices Passive or Generator-Type Telephone Transmitters

Last Update: 2011-05-30