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The AM-4979/GR is an amplified version of the popular LS-454/U loudspeakers. The speaker was designed for use with cryptographic equipment but can be easily employed with any radio. The design is water proof and features a mounting bracket as part of the enclosure. A 4 inches, 2 Watts, 8 Ohms permanent magnet cone type speaker, type LS-445/U is employed and input to the amplifier stage is of high impedance. The enclosure also includes a built in U-183/U audio connector for the addition of a microphone or handset. Internally, the AM-4979/GR incorporates an audio amplifier and support circuitry. The connecting audio cord is terminated with a U-229/U connector and is permanently affixed to the enclosure with a strain relief. DC power is supplied via an MS-3114E8-4S connector which is coupled with cable assembly CX-12925/U MODIFIED. The amplifier will not provide sidetone to the speaker during the transmit cycle and is muted by an internal relay. With a simple circuit modification, it is possible to provide sidetone during transmit.

AM-4979 GR schematic.jpg