SE7402969L - - Google Patents

Info

Publication number
SE7402969L
SE7402969L SE7402969A SE7402969A SE7402969L SE 7402969 L SE7402969 L SE 7402969L SE 7402969 A SE7402969 A SE 7402969A SE 7402969 A SE7402969 A SE 7402969A SE 7402969 L SE7402969 L SE 7402969L
Authority
SE
Sweden
Prior art keywords
output
earthing
key
exchange
currents
Prior art date
Application number
SE7402969A
Other languages
Unknown language ( )
Inventor
O Ala-Eddin
Original Assignee
Ericsson Telefon Ab L M
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 Ericsson Telefon Ab L M filed Critical Ericsson Telefon Ab L M
Priority to SE7402969A priority Critical patent/SE7402969L/
Priority to GB811175A priority patent/GB1494136A/en
Priority to DE19752508547 priority patent/DE2508547A1/en
Priority to IT2093075A priority patent/IT1033426B/en
Publication of SE7402969L publication Critical patent/SE7402969L/

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/42—Systems providing special services or facilities to subscribers
    • H04M3/58—Arrangements for transferring received calls from one subscriber to another; Arrangements affording interim conversations between either the calling or the called party and a third party

Abstract

1494136 Automatic exchange systems TELEFONAKTIEBOLAGET L M ERICSSON 26 Feb 1975 [6 March 1974] 8111/75 Heading H4K In an exchange system in which a subscriber makes an enquiry call, e.g. to initiate an interim conversation with a third party, by earthing one of the speech wires La, Lb, e.g. by depressing a key K at his substation TA, this earthing is detected at the exchange by a circuit DA which includes voltage dividers R5, R6 and R3, R4 and a differential amplifier DF. The resistors R3-R6 are chosen so that for on-hook (no current in La, Lb ) and connection-established (equal currents in La, Lb) conditions, the output from DF, Fig. 2 (not shown) is substantially zero. However, on depression of key K the currents in La, Lb become unequal, resulting in a negative output from DF. This output actuates a coupling circuit, which brings about the necessary switching sequences for an enquiry call.
SE7402969A 1974-03-06 1974-03-06 SE7402969L (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
SE7402969A SE7402969L (en) 1974-03-06 1974-03-06
GB811175A GB1494136A (en) 1974-03-06 1975-02-26 Telephone exchanges
DE19752508547 DE2508547A1 (en) 1974-03-06 1975-02-27 DETECTION CIRCUIT FOR TELEPHONE EXTENSIONS
IT2093075A IT1033426B (en) 1974-03-06 1975-03-05 REQUEST CALL DETECTOR IN TELEPHONE CONTROL UNITS

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE7402969A SE7402969L (en) 1974-03-06 1974-03-06

Publications (1)

Publication Number Publication Date
SE7402969L true SE7402969L (en) 1975-09-08

Family

ID=20320429

Family Applications (1)

Application Number Title Priority Date Filing Date
SE7402969A SE7402969L (en) 1974-03-06 1974-03-06

Country Status (4)

Country Link
DE (1) DE2508547A1 (en)
GB (1) GB1494136A (en)
IT (1) IT1033426B (en)
SE (1) SE7402969L (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL7904429A (en) * 1979-06-06 1980-12-09 Philips Nv FLOW DETECTION DEVICE FOR AN AUTOMATIC TELEPHONE CONTROL PANEL.
DE3108264C2 (en) * 1981-03-05 1984-05-30 Deutsche Fernsprecher Gesellschaft Mbh Marburg, 3550 Marburg Circuit arrangement for detecting the switching state of an earth button on a telephone set

Also Published As

Publication number Publication date
GB1494136A (en) 1977-12-07
DE2508547A1 (en) 1975-09-11
IT1033426B (en) 1979-07-10

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