GB704228A - Improvements in or relating to circuit-arrangements for use in automatic signalling systems - Google Patents

Improvements in or relating to circuit-arrangements for use in automatic signalling systems

Info

Publication number
GB704228A
GB704228A GB8820/52A GB882052A GB704228A GB 704228 A GB704228 A GB 704228A GB 8820/52 A GB8820/52 A GB 8820/52A GB 882052 A GB882052 A GB 882052A GB 704228 A GB704228 A GB 704228A
Authority
GB
United Kingdom
Prior art keywords
leg
loop
cathode
changes
current
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
GB8820/52A
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.)
Philips Electrical Industries Ltd
Original Assignee
Philips Electrical Industries 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 Philips Electrical Industries Ltd filed Critical Philips Electrical Industries Ltd
Publication of GB704228A publication Critical patent/GB704228A/en
Expired legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M1/00Substation equipment, e.g. for use by subscribers
    • H04M1/26Devices for calling a subscriber
    • H04M1/515Devices for calling a subscriber by generating or selecting signals other than trains of pulses of similar shape, or signals other than currents of one or more different frequencies, e.g. generation of dc signals of alternating polarity, coded pulses or impedance dialling

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Devices For Supply Of Signal Current (AREA)
  • Interface Circuits In Exchanges (AREA)

Abstract

704,228. Automatic exchange systems. PHILIPS ELECTRICAL INDUSTRIES, Ltd. April 7, 1952 [April 10, 1951], No. 8820/52. Class 40 (4) [Also in Group XXXVIII] In a system, e.g. for signalling digital information from a subscriber to a telephone exchange in which signals are transmitted to a receiver over a line loop by changing the value of the resistance inserted at the distant end of the loop, one leg a of the loop is connected to battery at the receiving end and the other leg b is connected to the cathode of a valve B1 the control electrode of which is fed with such a potential that the cathode remains substantially at earth potential irrespective of the value of the resistance inserted in the loop. This arrangement minimizes the errors due to leakage to earth in the line loop. Thus the current through the leak resistance of the leg b unlike that of the leg a passes through the signal receiver and may produce an erroneous operation therein. By maintaining the cathode of B1 at earth potential no current through the leakage resistance Rb of the leg b is permitted. The valve B 1 behaves as an earthed impedance equal to the reciprocal of its mutual conductance which is small compared with the values of the signalling resistors Rk1 ... Rk10 so that changes in current due to changes in these resistors produce only a small change in its cathode potential. This small change is however further reduced by the use of a negative feed backcircuit incorporating the valve B 2 . Changes in signalling current produce corresponding changes in voltage across the anode resistor R 1 which are detected by a known signal detector OI.
GB8820/52A 1951-04-10 1952-04-07 Improvements in or relating to circuit-arrangements for use in automatic signalling systems Expired GB704228A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL704228X 1951-04-10

Publications (1)

Publication Number Publication Date
GB704228A true GB704228A (en) 1954-02-17

Family

ID=19812023

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8820/52A Expired GB704228A (en) 1951-04-10 1952-04-07 Improvements in or relating to circuit-arrangements for use in automatic signalling systems

Country Status (2)

Country Link
DE (1) DE918512C (en)
GB (1) GB704228A (en)

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL73400C (en) * 1948-02-05

Also Published As

Publication number Publication date
DE918512C (en) 1954-09-27

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