| 摘要 |
A portable public address system for use in motor buses which can also be used inside buildings or out-of-doors including a first case and a second case. Within the first case, which is approximately the size of a pack of cigarettes, is an amplifier circuit with a Darlington configuration transistor pre-amplifier, a three-position switch, a volume control and a microphone. Within the second case is a loudspeaker and battery supply which are electrically connected to the amplifier circuit in the first case through the switch.
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