Title:
【発明の名称】拡声電話装置および該装置に用いる騒音抑圧回路
Document Type and Number:
Japanese Patent JP3076072
Kind Code:
B2
Abstract:
Controlled by a signal level produced by a microphone (12), a noise suppressing circuit (25) supplies a first attenuator (16) with a local level which is equal to the signal level and is suppressed to a predetermined output level when the signal level is lower and higher than a predetermined input level. Cooperating with a drive level produced by a second attenuator (17) to drive a loudspeaker (13), the local level makes a comparator unit (21-23) produce a control signal for making the first attenuator give smaller and greater amounts of attenuation to the signal level with the drive level rendered by the second attenuator low and high when positive and negative values are had, respectively, by an input difference equal to the local level less the drive level. Preferably, the local level is suppressed by a level difference had by the signal level above the predetermined input level.
Inventors:
Yutaka Tomiyori
Tadashi Eguchi
Tadashi Eguchi
Application Number:
JP4546391A
Publication Date:
August 14, 2000
Filing Date:
February 19, 1991
Export Citation:
Assignee:
NEC
Saitama NEC Corporation
Saitama NEC Corporation
International Classes:
H04M1/60; H04M9/08; H04M9/10; (IPC1-7): H04M1/60
Domestic Patent References:
| JP59230356A | ||||
| JP1212950A |
Attorney, Agent or Firm:
Naoki Kyomoto