Miniature portable public address system
US4090033A · kind A · utility
11Cited by
2References
8Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | May 24, 1976 |
| Grant date | May 16, 1978 |
| Priority date | — |
| Expiry date | May 24, 1996 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04R27/04
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.