GB874254A - Digit sending equipment for telephone substations - Google Patents

Digit sending equipment for telephone substations

Info

Publication number
GB874254A
GB874254A GB3408458A GB3408458A GB874254A GB 874254 A GB874254 A GB 874254A GB 3408458 A GB3408458 A GB 3408458A GB 3408458 A GB3408458 A GB 3408458A GB 874254 A GB874254 A GB 874254A
Authority
GB
United Kingdom
Prior art keywords
exchange
line
voltage
polarity
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
GB3408458A
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.)
STC PLC
Original Assignee
Standard Telephone and Cables PLC
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 Standard Telephone and Cables PLC filed Critical Standard Telephone and Cables PLC
Publication of GB874254A publication Critical patent/GB874254A/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
    • H04M1/26—Devices for calling a subscriber
    • H04M1/515—Devices 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q3/00—Selecting arrangements

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Monitoring And Testing Of Exchanges (AREA)
  • Interface Circuits In Exchanges (AREA)

Abstract

874,254. Automatic current-control systems. STANDARD TELEPHONES & CABLES Ltd. Oct. 24, 1958 [net. 26, 1957], No. 34084/58. Class 38 (4). [Also in Group XXXIX] In a sub-station arrangement in which a subscriber signals digits to the exchange by causing the line current to assume one of a plurality of discrete values, a zener diode provides a constant reference voltage which in combination with selected resistance values determines the line current, which is thereby rendered independent of variations in line resistance or exchange voltage. The invention is applied to a system in which the exchange makes two successive tests, for each signal, by applying first one polarity and then the other to the line. Pushbuttons close switches S 2 . . .S 6 in various combinations indicative of the digit, the switches S 2 , S 4 switching resistances Wi 1 or Wi 2 into the emitter circuit of the transistor Tr when the exchange polarity is positive and S 3 , S 5 switching in these resistors when the exchange polarity is negative. For either polarity the zener diode Z is across the line, and the voltage across the resistor or resistors in the emitter circuit is maintained at the breakdown voltage. The emitter current and hence the line current is thus determined solely by the zener voltage and the resistance in the emitter circuit.
GB3408458A 1957-10-26 1958-10-24 Digit sending equipment for telephone substations Expired GB874254A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEST13096A DE1046109B (en) 1957-10-26 1957-10-26 Circuit arrangement for a telephone station for carrying out the key selection according to the voltage comparison method

Publications (1)

Publication Number Publication Date
GB874254A true GB874254A (en) 1961-08-02

Family

ID=7455939

Family Applications (1)

Application Number Title Priority Date Filing Date
GB3408458A Expired GB874254A (en) 1957-10-26 1958-10-24 Digit sending equipment for telephone substations

Country Status (4)

Country Link
BE (1) BE572410A (en)
DE (1) DE1046109B (en)
GB (1) GB874254A (en)
NL (1) NL232514A (en)

Also Published As

Publication number Publication date
DE1046109B (en) 1958-12-11
NL232514A (en)
BE572410A (en)

Similar Documents

Publication Publication Date Title
US4306119A (en) Telephone outpulsing circuit
GB982825A (en) Class of service telephone system
US2810081A (en) Electronic switch for selectively blocking or permitting the simultaneous transmission of signals in two channels
US3692947A (en) Time division switching system conference circuit
US3973084A (en) Electric impulse transmitters for telephone instruments
SE7705441L (en) DEVICE FOR TELEPHONE SYSTEMS
US3821486A (en) Bridge type supervisory detector with reduced breakdown voltage requirements
GB874254A (en) Digit sending equipment for telephone substations
US3828139A (en) Disconnect circuit for telephone systems
US2967212A (en) Identifying testing or discriminating device
GB1456250A (en) Matrix control circuit
US2829205A (en) Duplex signaling circuit
CH387107A (en) Circuit arrangement for switching off the ringing current in the event of subscriber reporting in telephone systems
GB876983A (en) Translator for a telephone system
US4058770A (en) Solid state subscriber selection switches for wired broadcasting systems
GB1113234A (en) Improvements relating to automatic telecommunication switching systems
GB994458A (en) Improvements relating to circuit arrangements employing semi-conductor diodes
GB1353282A (en) Circuit for detecting signals transmitted onto a two wire line
IE41644L (en) Power supply circuits
US3439191A (en) Timing circuit
US3140407A (en) Pulse shaper employing means to control time constant of included differentiator circuit
GB1037676A (en) Improvements in electrical signalling systems employing sampling arrangements
GB1516906A (en) Circuit for supplying impulses from a telephone instrumen
GB868054A (en) Improvements in or relating to telephone sub-sets
GB737778A (en) Arrangement in an automatic telecommunication exchange, for determining to which of a plurality of service classes a desired connection between two subscribers belongs