GB2021355A - Hands-free facility - Google Patents

Hands-free facility

Info

Publication number
GB2021355A
GB2021355A GB7911901A GB7911901A GB2021355A GB 2021355 A GB2021355 A GB 2021355A GB 7911901 A GB7911901 A GB 7911901A GB 7911901 A GB7911901 A GB 7911901A GB 2021355 A GB2021355 A GB 2021355A
Authority
GB
United Kingdom
Prior art keywords
circuit
hands
instrument
transmit
switch
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB7911901A
Other versions
GB2021355B (en
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
International Standard Electric Corp
Original Assignee
International Standard Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by International Standard Electric Corp filed Critical International Standard Electric Corp
Publication of GB2021355A publication Critical patent/GB2021355A/en
Application granted granted Critical
Publication of GB2021355B publication Critical patent/GB2021355B/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/68—Circuit arrangements for preventing eavesdropping
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/60—Substation equipment, e.g. for use by subscribers including speech amplifiers
    • H04M1/6033—Substation equipment, e.g. for use by subscribers including speech amplifiers for providing handsfree use or a loudspeaker mode in telephone sets

Abstract

An anti-eavesdropping circuit AS for a telephone subscriber's instrument of the hands-free type and provided with voice switched means (ST) responsive for speech detectors (D1, D2, for operating variable gain transmit and receive amplifiers (RV1; RV2). The circuit AS is coupled to the transmit amplifier control output of the voice switched means (ST) through a threshold device (SS) which detects when the transmit amplifier (RV1) is on for a predetermined time eg 305 and initiates a timer (Z) which connects an alarm signal from a generator (Q) to an audible warning device (W) via a switch (A). A switch (T) for disabling circuit (AS) is provided. The circuit (AS) may be connected to the receive amplifier (RV2) and it may employ the loudspeaker (LS) of the subscriber's instrument as a warning device. <IMAGE>
GB7911901A 1978-05-20 1979-04-05 Hands-free facility Expired GB2021355B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19782822069 DE2822069C2 (en) 1978-05-20 1978-05-20 Circuit arrangement for protection against eavesdropping in voice-controlled hands-free devices, in particular in telephone sets

Publications (2)

Publication Number Publication Date
GB2021355A true GB2021355A (en) 1979-11-28
GB2021355B GB2021355B (en) 1982-06-03

Family

ID=6039819

Family Applications (1)

Application Number Title Priority Date Filing Date
GB7911901A Expired GB2021355B (en) 1978-05-20 1979-04-05 Hands-free facility

Country Status (4)

Country Link
BR (1) BR7902952A (en)
DE (1) DE2822069C2 (en)
GB (1) GB2021355B (en)
IE (1) IE48335B1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2122454A (en) * 1982-05-21 1984-01-11 Mitel Corp Loudspeaking telephone

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE339704B (en) * 1970-12-22 1971-10-18 Ericsson Telefon Ab L M

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2122454A (en) * 1982-05-21 1984-01-11 Mitel Corp Loudspeaking telephone

Also Published As

Publication number Publication date
IE790973L (en) 1979-11-20
DE2822069A1 (en) 1979-11-22
BR7902952A (en) 1979-11-27
DE2822069C2 (en) 1986-02-20
GB2021355B (en) 1982-06-03
IE48335B1 (en) 1984-12-12

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Legal Events

Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee