GB889840A - Improvements in or relating to telephone apparatus - Google Patents

Improvements in or relating to telephone apparatus

Info

Publication number
GB889840A
GB889840A GB1805459A GB1805459A GB889840A GB 889840 A GB889840 A GB 889840A GB 1805459 A GB1805459 A GB 1805459A GB 1805459 A GB1805459 A GB 1805459A GB 889840 A GB889840 A GB 889840A
Authority
GB
United Kingdom
Prior art keywords
transistor
winding
conductive state
indicator lamps
relay
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.)
Expired
Application number
GB1805459A
Inventor
John Lynn Golding
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.)
Telephone Manufacturing Co Ltd
Original Assignee
Telephone Manufacturing Co Ltd
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 Telephone Manufacturing Co Ltd filed Critical Telephone Manufacturing Co Ltd
Priority to GB1805459A priority Critical patent/GB889840A/en
Publication of GB889840A publication Critical patent/GB889840A/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/60—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors
    • H03K17/64—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors having inductive loads

Landscapes

  • Emergency Alarm Devices (AREA)

Abstract

889,840. Manual switchboards. TELEPHONE MANUFACTURING CO. Ltd. May 26, 1960 [May 27, 1959], No. 18054/59. Class 40 (4). [Also in Group XL (c)] A night or other supervisory alarm for a telephone switchboard has the indicator lamps connected in series with a resistor R1 included in the base-emitter circuit of transistor TR, the latter being normally in a non-conductive state, so that when any of the indicator lamps are energized the subsequent voltage drop across R1 is sufficient to cause the transistor to conduct and a pilot relay RL in the collector circuit of the transistor to be actuated. A germanium diode GD is shunted across the winding of the relay RL to prevent the developement of a back e.m.f. across the winding when the transistor switches back to its initial non- conductive state.
GB1805459A 1959-05-27 1959-05-27 Improvements in or relating to telephone apparatus Expired GB889840A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1805459A GB889840A (en) 1959-05-27 1959-05-27 Improvements in or relating to telephone apparatus

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1805459A GB889840A (en) 1959-05-27 1959-05-27 Improvements in or relating to telephone apparatus

Publications (1)

Publication Number Publication Date
GB889840A true GB889840A (en) 1962-02-21

Family

ID=10105844

Family Applications (1)

Application Number Title Priority Date Filing Date
GB1805459A Expired GB889840A (en) 1959-05-27 1959-05-27 Improvements in or relating to telephone apparatus

Country Status (1)

Country Link
GB (1) GB889840A (en)

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