EP 0096778 B1 19880817 - MICROPHONE
Title (en)
MICROPHONE
Publication
Application
Priority
DE 3222295 A 19820614
Abstract (en)
[origin: US4541112A] An electroacoustic transducer system comprises a microphone working into a low-frequency amplifier for the energization of an a-c load such as, for example, a loudspeaker or a volume indicator at a control panel. Biasing voltage for the microphone and operating current for the amplifier are derived from a d-c source, via a phantom circuit including the output leads of the amplifier and through a coupler in cascade with a chopper; the latter includes a transistor conducting intermittently under the control of an adjustable pulse generator whose pulse width is varied by negative feedback from the integrated chopper output. An output transformer with a primary in series with the transistor has several secondaries each connected across a storage capacitor through a diode for the generation of a relatively high biasing voltage for the microphone, a relatively low driving voltage for the amplifier and, possibly, a further voltage used to vary the directional pattern of the microphone. To facilitate the establishment of different voltage levels, the development of the lower voltage is delayed-by the combination of a choke with a Zener diode, or by a thyristor-until the higher voltage has been reached by a transient occurring at the beginning of each cutoff phase.
IPC 1-7
IPC 8 full level
H02M 3/335 (2006.01); H04R 3/00 (2006.01); H04R 19/04 (2006.01)
CPC (source: EP US)
H04R 3/00 (2013.01 - EP US); H04R 19/04 (2013.01 - EP US)
Designated contracting state (EPC)
AT BE CH DE FR GB IT LI NL SE
DOCDB simple family (publication)
EP 0096778 A2 19831228; EP 0096778 A3 19851204; EP 0096778 B1 19880817; AT E36629 T1 19880915; DE 3377765 D1 19880922; US 4541112 A 19850910
DOCDB simple family (application)
EP 83105247 A 19830526; AT 83105247 T 19830526; DE 3377765 T 19830526; US 50430983 A 19830614