WO1994028667A1 - Systeme d'alimentation d'un telephone en courant - Google Patents

Systeme d'alimentation d'un telephone en courant Download PDF

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Publication number
WO1994028667A1
WO1994028667A1 PCT/GB1994/001144 GB9401144W WO9428667A1 WO 1994028667 A1 WO1994028667 A1 WO 1994028667A1 GB 9401144 W GB9401144 W GB 9401144W WO 9428667 A1 WO9428667 A1 WO 9428667A1
Authority
WO
WIPO (PCT)
Prior art keywords
telephone
power supply
supply system
voltage
current
Prior art date
Application number
PCT/GB1994/001144
Other languages
English (en)
Inventor
Ian Adrian Tapping
Rodney Barker Hale
Original Assignee
Chesilvale Electronics Limited
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 Chesilvale Electronics Limited filed Critical Chesilvale Electronics Limited
Priority to AU68010/94A priority Critical patent/AU6801094A/en
Publication of WO1994028667A1 publication Critical patent/WO1994028667A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M19/00—Current supply arrangements for telephone systems
    • H04M19/08—Current supply arrangements for telephone systems with current supply sources at the substations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M9/00—Arrangements for interconnection not involving centralised switching
    • H04M9/02—Arrangements for interconnection not involving centralised switching involving a common line for all parties

Definitions

  • the present invention relates to a telephone power system. It particularly relates to means for permitting communication between telephone instruments on otherwise unpowered cable pairs. It may provide a series connected and regulated DC and ringing current supply.
  • An embodiment of the invention can be cost effective and simple. It may be in the form of a self-contained system (a "box") for connection to a telephone system.
  • the "box” may include a test telephone for connection to a telephone system comprising a conductor pair and a remote telephone instrument.
  • a local battery telephone In this case the telephone has within its housing a battery to provide a DC supply to operate the telephone. This need only be of low voltage and current capability. Another local battery type telephone is required at the other end, it is not possible to communicate with a standard telephone (e.g. a telephone of a service subscriber).
  • the invention provides in a first of its aspects, a telephone power supply system comprising a constant current, low impedance power supply adapted for series connection into a telephone speech circuit.
  • the power supply system according to the invention may be employed for automatically regulating current flowing in the speech circuit to a suitable level, irrespective (within bounds) of the condition of the types and condition of the telephone instruments and of interconnecting cables to ensure satisfactory generation of the telephone instruments.
  • the power supply system preferably includes means to detect an open circuit condition of the speech circuit and to cause the power supply switch to a stand-by condition for such time as an open circuit condition persists, this arrangement preventing waste of power caused by the power supply attempting to drive current around an open circuit.
  • the power supply system may additionally include a ringing-signal generator and means for selectively connecting it to the speech circuit.
  • the power supply system is operative to regulate current in the speech circuit at a level close to the minimum required to secure satisfactory operation of a telephone instrument connected thereto.
  • current level may vary between countries, telephone systems, and/or service providers.
  • the power supply system comprises a current regulated power source in parallel with a capacitor, the capacitor providing a low-impedance path for speech signals.
  • the current regulated power supply may comprise a variable voltage source with feedback means (such as a resistor and means to detect a voltage across it) operable to vary the voltage according to variations in the magnitudes of current generated by the voltage.
  • the voltage source may include a battery and a variable voltage multiplier.
  • the current regulated power supply may be arranged to provide a substantially constant current under normal operating conditions.
  • the invention provides a telephone power supply unit comprising a power supply system according to the first aspect of the invention and connection means for connecting the unit to a speech circuit.
  • the invention provides a telephone communication apparatus comprising a telephone instrument connected in series with a telephone power supply system according to the first aspect of the invention.
  • the invention further provides, in a fourth aspect, a telephone system comprising first and second telephone instruments and a telephone power supply system according to the first aspect of the invention connected in series.
  • the system includes a ringing signal generator and switch means for selectively connecting it to a cable pair that connects at least one of the telephone instruments.
  • the means for detecting feedback voltage includes a detector for detecting an open circuit condition of the cable pair and switching the power system to a standby condition to reduce battery consumption.
  • a preferred embodiment of the invention is a box which may be connected to the line in a simple way to permit the transmission of a DC supply to local and distant telephones and to permit the alerting of the distant telephone by means of an AC ringing signal typical of that generated by the Exchange (CO. ) equipment. It is desirably of high efficiency at all times thus limiting battery and therefore case size.
  • the box (hereafter referred to as the Talk/Ringdown box) must not generate any adverse conditions not normally seen on a working telephone line.
  • the unit must be capable of driving a raised voltage grater than is typically available from commercially available batteries or alternatively be able to drive greater than the minimum current necessary to operate the distant and local telephones.
  • the voltage multiplier is placed in series with the line and the local and distant telephones. In this presentation it will be configured to yield the lowest possible series impedance to the AC speech signals on the line. Ideally this means the Talk/Ringdown box will be transparent to voice signals.
  • the output current will be regulated to produce a current- just above the minimum necessary to operate the telephones. This may be achieved by placing a low value monitoring resistor in series with the output winding of the DC supply. The voltage appearing across the resistor provides a feedback to the primary section of the power supply to limit the » power generated in the output.
  • the invention will normally include a circuit arrangement that detects an open-circuit output and which will limit the input drive to conserve power. To ring the distant end, the user will press a push ⁇ button to disconnect the DC series supply and connect an AC ringing current generator to the output terminals connected to the distant telephone. This feature is desirable but not essential.
  • This design may be configured as a separate box or may be incorporated as circuit element in another product requiring a local battery/battery transmitting feature and this may be incorporated with or without the ringing circuit.
  • the Talk/Ringdown box may be enhanced by adding to it telephony capability through the addition of a transmitting and receiving means, typically a handset, headset or hands-free loudspeaking telephone.
  • Embodiments may optionally include other features such as visual function indicators, battery fail indicators, and/or audible function indicators.
  • Figure 1 is a schematic circuit diagram of a telephone system being a first embodiment of the invention.
  • Figure 2 is a schematic circuit diagram of a telephone power supply unit being a second embodiment of the invention. Modes for Carrying out the Invention
  • the circuit shown in Fig. 1 provides a speech battery to local and distant telephones and the capability to ring the distant telephone.
  • the telephone system comprises a power supply unit A, a first telephone instrument 11, a second telephone instrument 12 and first and second cable pairs B, C interconnecting the power supply unit and, respectively, the first and second telephone instruments 11, 12, the first instrument 11 being local and the second (12) being distant.
  • the power supply unit A is connected to the first cable pair B by connector means 13, 13' which may conveniently, comprise a pair of 4mm plugs and sockets.
  • the power supply unit A may be provided in a combined "box" with the first telephone instrument 11 in which case the instrument 11 may typically be directly connected to the power supply unit A.
  • Second connector means 14, 14' (again, conveniently 4mm plugs and sockets) are provided for external connection to the cable pair B for connection of the unit A to the second instrument B.
  • the power supply unit A will now be described.
  • a conductor 30 interconnects one pole of each of the connector means 13, 14 to complete a first half of the circuit between the telephone instruments 11, 12, providing a direct electrical connection between one cable of the two cable pairs B,C.
  • a second half of the circuit is completed by the power supply system (to be described) which interconnects the other cable of each cable pair B, C, and is connected between connectors 13' and 14' .
  • the power supply system includes a capacitor 10 which interconnects the connectors 13' and 14'.
  • the capacitor 10 provides a low-impedance path for a.c. speech signals between the telephone instruments 11, 12 and smooths and decouples the output of the voltage multiplier described below.
  • the power supply system further includes a constant current power supply which is connected in parallel with the capacitor 10.
  • the constant current power supply includes a battery set 1 across which is connected a primary winding 3 of a step-up transformer in series with a transistor 5. Also connected across the battery set 1 is a P M, square wave, pulse generator 2, the output pulses of which are pulse- width modulated in dependence upon the voltage on an input line 8. The output of the pulse generator 2 is connected to the gate of the transistor 5.
  • the circuit is arranged such that pulses of current are caused to flow through the primary winding 3, under the control of the transistor 5, in synchronism with the pulses generated by the pulse generator 2, such that the average voltage appearing at the secondary winding 4 of the transformer varies with the width of the generated pulses.
  • the secondary winding 4 of the transformer is connected to a bridge rectifier 6, the more negative output of which is connected to the negative side of the battery set 1, and the more positive output of which is connected to a ringing circuit 15.
  • a connection is also made between the ringing circuit 15 and the negative output of the bridge rectifier 6.
  • a two-pole, two-way ganged switch 16a, 16b selectively connects an input of the ringing circuit 15 to the output of the pulse generator 2 through normally- open contacts 16a.
  • An output of the ringing circuit 15 is connected through the switch either (through normally- closed contacts) to the capacitor 10 or, through a capacitor 17, to the conductor 30.
  • a resistor 7 connects the negative output of the bridge rectifier 6 to the output terminal 14'.
  • a connection is made from the resistor 7, through a detector circuit 18, an output of which is connected to the control input of the pulse generator 2.
  • a second output of the detector 18 is fed to a stand-by input 19 of the pulse generator.
  • output from the rectifier 15 is fed through the ringing circuit 15 to the switch at 16b.
  • a DC power circuit is formed from the bridge rectifier 6, through the ringing circuit 15, the switch 16b, and the connector 13', to the first telephone instrument 11, via the cable pair B.
  • the circuit continues through the cable pair B, the connector 13, the conductor 30, and connector 14 to the cable pair C and the second telephone instrument
  • the circuit is competed through the cable pair C, the connector 14', the resistor 7, finally returning to the bridge rectifier 6.
  • the capacitor 10 is effectively connected (through the resistor 7) across the output of the bridge rectifier 2.
  • a voltage appearing across the resistor 7 will be detected by the detector 18.
  • the detector 18 will generate an output signal, fed to the pulse generator through its control input 8.
  • the pulse generator 2 modulates the width of its pulses (and thus the output voltage of the bridge rectifier 6) to maintain the current flowing through the series circuit (as detected by the resistor 7) at a substantially constant level, irrespective of the resistance or load within the circuit.
  • the ringing circuit 15 When the switch 16a, 16b is operated, the ringing circuit 15 is connected in series to the second telephone instrument 12 through the resistor 7, the capacitor 17, connectors 14, 14' and the second cable pair C. Through this connection path, the ringing circuit applies a ringing signal to the second telephone instrument.
  • FIG. 2 shows a telephone power supply unit which includes a constant-current power supply D.
  • the constant current power supply D includes a battery set 101 connected between positive and negative supply lines +V, -V.
  • a PWM driver 102 being a square wave pulse generator with variable pulse width and repetition rate, is connected between the supply lines +V, -V.
  • Also connected between the supply lines +V, -V is an inductor 104 in series with a transistor 103 which is also connected to the negative supply line -V.
  • the gate of the transistor 103 is connected to a pulse output of the PWM driver 102.
  • a diode 105 is connected by its cathode to a common point between the inductor 104 and the transistor 103.
  • a reservoir capacitor 106 is connected between the positive supply line +V and the anode of the diode 105.
  • the PWM driver 102 switches the transistor 103 on and off. As the transistor 103 turns off, it breaks the current flow though the inductor 104, which causes a large back-EMF to be generated. This charges the reservoir capacitor 106 through the diode 105.
  • a DC output voltage is generated between the anode of the diode (at voltage V ⁇ en _ ) and the positive supply line +V (at voltage V Qen+ ) .
  • the voltage V ⁇ en is dependent upon the pulse width and pulse repetition rate of the PWM generator 102.
  • This output voltage is filtered and smoothed by a resistor 107, a first side of which is connected to the cathode of the diode 105 and a second side of which is connected through a capacitor 108 to the positive supply line +V.
  • the capacitor 108 also provides a low-impedance path for speech signals.
  • a feedback resistor 109A connects a first output of the constant current power supply D at point X in Figure 2 to a common point Y between the resistor 107 and the capacitor 108.
  • a second output of the power supply is taken from point Z at the positive supply line +V.
  • a feedback line 112 feeds back the voltage at the first output X of the power supply D to the PWM generator 102.
  • a feedback line 114 feeds back the voltage _ to the PWM generator 102.
  • the PWM generator 102 adjusts the width and repetition rate of its pulses to maintain the voltage of the first output X at a constant level.
  • the voltage of the first output X is proportional to the current through the feedback resistor 109A, so the effect of this is that the power supply D attempts to maintain a constant current through the feedback resistor 109A.
  • the voltage at the first output X together with the voltage ⁇ en _, are fed to the inputs of a comparator 120, the output of which is fed to a stand-by input 119 of the PWM generator 102.
  • Vgen- a condition that occurs only when no current is passing through the feedback resistor 109A
  • the output from the comparator 120 changes to drive the PWM generator 102 into a stand-by state in which it generates only a low voltage.
  • the comparator 120 reverts to its previous state, and the power supply D once again enters constant-current mode.
  • the telephone power supply unit additionally includes a ringing-signal generator for ringing a remote telephone connected to the unit.
  • the ringing-signal generator comprises a bridge or push-pull driver generator 110 which generates a square-wave output, typically at 25Hz.
  • the driver generator is driven by an oscillator 117 are powered by the voltage multiplier.
  • a push-switch 118 is provided which activates the oscillator 117 and the drive generator 110 on activation thereof by a user.
  • the telephone power supply unit has local connections 115A, 115B for connection through a first cable pair to a first telephone instrument, and distant connections 116A, 116B for connection through a second cable pair to a remote telephone instrument.
  • Connectors 115A and 116A are connected, respectively to the second and first outputs Z, X of the constant-current power supply D.
  • Connector 115B is connected to a normally- closed contact of a relay RLl, a common contact of the relay RLl being connected through a resistor 109B to the connector 116B. (The resistor 109B is optionally provided to balance the line. )
  • the local and remote telephone instrument are normally connected together in series with the constant-current power supply D through the relay RLl.
  • a normally-open contact of the relay RLl is connected to the output of the driver-generator 110.
  • the push-switch 118 additionally, on operation, (by means not shown) causes energisation of the coil of the relay RLl such that the output of the driver generator 110 becomes connected to the remote telephone instrument though the relay RLl, so causing that telephone instrument to ring.
  • this circuit may optionally be switched by the ring key to a higher voltage Vgen or a bridge driver output may be used to generate 100V peak to peak.
  • Vgen voltage
  • a bridge driver output may be used to generate 100V peak to peak.
  • an LED indicator may be placed in series with the DC path so that when current flows the LED will light to indicate off-hook.
  • the arrangement described ensures that the output voltage achieved is sufficient to drive the minimum current necessary to operate a telephone properly at any local line length within the operating range of the system. This would typically be 6-10km, and a typical current of 25mA.
  • telephone instrument as used herein is intended to include any telephone speech transmitting or receiving apparatus such as, for example, a conventional domestic telephone, a test telephone, a headset, a handset, and so forth.
  • the telephone function at 11 may optionally be included in the box in a number of ways, including but not exclusively as a handset/headset or by the addition of a hands-free loudspeaker system.
  • the Talk/Ringdown box functions may be built into another product requiring these features, e.g. a test telephone which may thus constitute a local telephone.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Devices For Supply Of Signal Current (AREA)

Abstract

Un système d'alimentation en courant, destiné à un téléphone, comprend une alimentation (D) en courant constant connectée en série à un circuit d'interconnexion de deux postes téléphoniques. L'alimentation en courant peut comprendre un multiplicateur de tension contenant un transformateur. Selon une variante, un multiplicateur de tension peut comprendre un inducteur (104) pompé par un générateur (102) à modulation d'impulsions en largeur (PWM) ainsi qu'un transistor (103). Un dispositif (110, 107, 108, RL1) de génération de signal d'appel peut également être utilisé. Le circuit comprend de préférence un moyen (120) permettant de détecter un état de circuit ouvert, dans lequel cas le circuit est commuté en mode d'attente.
PCT/GB1994/001144 1993-05-26 1994-05-26 Systeme d'alimentation d'un telephone en courant WO1994028667A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU68010/94A AU6801094A (en) 1993-05-26 1994-05-26 Telephone power system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB939310812A GB9310812D0 (en) 1993-05-26 1993-05-26 Telephone power system
GB9310812.4 1993-05-26

Publications (1)

Publication Number Publication Date
WO1994028667A1 true WO1994028667A1 (fr) 1994-12-08

Family

ID=10736128

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1994/001144 WO1994028667A1 (fr) 1993-05-26 1994-05-26 Systeme d'alimentation d'un telephone en courant

Country Status (3)

Country Link
AU (1) AU6801094A (fr)
GB (1) GB9310812D0 (fr)
WO (1) WO1994028667A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4683351A (en) * 1985-10-04 1987-07-28 Gte Communication Systems Corporation Impedance maintenance circuit for telephone interface
EP0259247A1 (fr) * 1986-08-26 1988-03-09 KRONE Aktiengesellschaft Circuit pour un appareil téléphonique
JPH0442689A (ja) * 1990-06-08 1992-02-13 Mitsubishi Electric Corp 給電制御装置

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4683351A (en) * 1985-10-04 1987-07-28 Gte Communication Systems Corporation Impedance maintenance circuit for telephone interface
EP0259247A1 (fr) * 1986-08-26 1988-03-09 KRONE Aktiengesellschaft Circuit pour un appareil téléphonique
JPH0442689A (ja) * 1990-06-08 1992-02-13 Mitsubishi Electric Corp 給電制御装置

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"Portable Telephone/intercom for Underground Mines - NTN-77/0919", TECHNOLOGY NEWS FROM THE BUREAU OF MINES U.S. DEPARTMENT OF THE INTERIOR, no. 34, June 1977 (1977-06-01), WASHINGTON D.C. - USA *
PATENT ABSTRACTS OF JAPAN vol. 16, no. 227 (E - 1207) 26 May 1992 (1992-05-26) *

Also Published As

Publication number Publication date
AU6801094A (en) 1994-12-20
GB9310812D0 (en) 1993-07-14

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