AU597420B2 - Electronic holding for two-loop telephones supplied via the subscriber line - Google Patents

Description

%1 597420 S F Ref: 32820 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION 'Ibhis dJwunert thean sIb amendments made under Sectooh 49.

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(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: a I4 S Name and Address *4 of Applicant: Address for Service: Address for Service: Siemens Aktiengesellschaft Wittelsbacherplatz 2 D-8000 Munich 2 FEDERAL REPUBLIC OF GERMANY Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia L( i Complete Specification for the invention entitled: Electronic Holding for Two-Loop Telephones Supplied Via The Subscriber Line The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3 i

ABSTRACT:

ELECTRONIC HOLDING CIRCUITS FOR TWO-LOOP TELEPHONES SUPPLIED VIA THE SUBSCRIBER LINE: The invention relates to electronic holding circuits for a microprocessor-controlled two-loop telephone supplied via the subscriber line, comprising a push-button block for subscriber dialling and special services.

One object of the invention is to construct the holding circuit using simple, integrable switching means, where the control elements consist only of push-button elements designed only for relatively low currents and which require no structural outlay.

«t c This aim is fulfilled in that push-buttons of the push-button block are used to emit impulses to the microcomputer, which emits Ol pulses to control the connection and disconnection of a current path with a load resistor between the a/b-wires of the respective subscriber line, optically-controlled transistor elements being o o99 @0 used to decouple the station and the subscriber line in respect of high voltage.

The invention can additionally be used in two-loop telephones with facilities for consultation calls and broker's calls.

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1C.- ELECTRONIC HOLDING CIRCUITS FOR TWO-LOOP TELEPHONES SUPPLIED VIA THE SUBSCRIBER LINE: The invention relates to electronic holding circuits for a two-loop telephone with microprocessor control, supplied via the subscriber line, a separate rectifier bridge being provided in respect of each subscriber line for reverse-polarity protection, a push-button block for subscriber dialling and special functioning, and th2 requisite speech circuit, together with a change-over device for switching over from one subscriber line to the other.

10 Telephone stations of the above-described type are referred ata to as two-loop telephones (Two-loop telephones, Operating manual S. FeTAp2-716-719, published by the German Post Office), the individual subscriber lines being selectively connected by means of locking pusho buttons, for example, and holding resistors which are required between the a/b-wires in the case of a consultation call or a broker's call are 9 connected and disconnected by means of push-button or relay contacts.

When the contacts of locking push-buttons are used, a structural outlay is required both for the connection and the disconnection of a holding resistor. The implementation of the switching 20 procedures using relays requires a relatively high switching power which, in the case of line-supplied telephone stations, is either not available at all, or cannot be made available sufficiently rapidly.

One object of the present invention is to provide a circuit arrangement for a holding circuit of the kind referred to above, which can be fully energised with a very low power consumption, and which can be fully controlled with a low input power, the subscriber line and the speech circuit of the telephone station being fully decoupled from one another in respect of high voltage, and control of the holding circuit can be readily triggered by switching means provided at the telephone station and designed to switch only very low-powered signals.

In accordance with the present invention there is provided, in a two-loop telephone supplied via a subscriber line, comprising a microprocessor control unit, a rectifier bridge for reverse polarity protection in the subscriber line, a push-button block for subscriber dialling, for emitting pulses to the microprocessor and special functions, and a requisite speech circuit including a change-over device for switching over from one subscriber line to another, wherein the microprocessor control unit controls connection and disconnection of a circuit path between wires forming the subscriber line in response to said impulses; an electronic holding circuit provided between the wires of the subscriber line, consisting of the series combination of a respective optically-driven ,:15 thyristor, a load resistor and a series transistor, base current for the "i *series transistor being branched from holding current of the associated I thyristor, which has a respective transistor opto-coupler serving as switch arranged in the base circuit, and both the thyristor and the transistor opto-coupler in each case being connectable via a control line to control outputs of the microprocessor control unit for activation when the changeover device switches from one subscriber line to another.

r, This results in the advantage that the unit which connects and disconnects the holding resistors can be designed in a simple fashion °o without additional structural outlay, without power-resistance switching means, and with integrable elements.

The invention will now be described with reference to the drawing, which is a simplified block-schematic diagram of one exemplary embodiment.

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*ttc1 3 The illustrated embodiment has a speech circuit SS of a telephone station comprising a microprocessor M, two make-and-break contacts, 11 and 12, for selectively connecting two subscriber lines, I or II, two rectifier bridge circuits, Gil and G12, and two holding circuits, H1 and H2. The holding circuits H1 and H2 each consist of an optically-driven thyristor, Tyl or Ty2, a respective load resistor, RL1 or RL2, a respective series transistor, T1 or T3, a respective transistor opto-coupler, T2 or T4, a respective holding circuit C1/R1 or C2/R2, and two pairs of drive points, ml/m2 and m3/m4.

The function of the circuit arrangement is as follows.

When the circuit arrangement for the holding circuit is in the rest state, for both the two subscriber lines the thyristors Tyl and Ty2 and the series transistors T1 and T3 occupy the blocked state. Depending upon the position of the connecting contacts, 15 11 and 12, the subscriber line I or II is connected. It has been assumed in the drawing that the subscriber line I is connected, and that a telephone connection can be established via the subscriber line I by means of the push-button block. It will be assumed that when the connection has been established, a consultation call is to take 20 place via the subscriber line II, and that in order to implement this call the operator actuates a function push-button that is specially provided for this purpose on the push-button block. In dependence upon the instantaneous operating state of the telephone station, the microprocessor M recognises the subscriber's request, i.e. that the current siezed subscriber line I is to remain seized in the holding state and that a consultation connection is to be established via the subscriber line II. In a manner (not shown) the subscriber t i 1~~1 1.1

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1 f( 4 *i If t III 6* 4l 4 line I is disconnected from the speech circuit SS and the subscriber line II is connected for the establishment of a connection via the make-and-break contacts 11/12. To enable the subscriber line I to remain held, the holding circuit Hi must now be actuated. This actuation of HI takes place shortly before disconnection of the subscriber line I from the speech circuit SS by means of the microprocessor M. Via the terminal point ml of the holding circuit the microprocessor M causes a pulse to be transmitted to the opticallycontrolled, and thus optically-ignitable, (UB operating voltage) thyristor Tyl, whereby Tyl switches conductive and remains conductive due to a holding current governed via C1 and R1. The current path for the d.c. current connected via the rectifier Gil extends across the tyristor Tyl, the load resistor RL1 and the series transistor T1, as the latter is switched conductive. In order that T1 may 15 be switched conductive, part of the holding current of Tyl is branched off and serves as a base current for tl. thus the load resistor R1 is actuated in the direction of the telephone exchange, whereby the subscriber line Ti (al/bl) is maintained in the held state. For example, if the subscriber line I is now to be re-connected in order to continue the conversation, and the subscriber line II is to be brought into the rest state (broker's call), this is again initiated by signalling via the push-button block to the microprocessor M. The make-and-break contacts 11/12 switch over. At the same time a pulse is emitted to the terminal point m2 of the holding circuit H1, as a result of which the transistor opto-coupler T2 is switched through. As a result the base current for the series transistor T1 is shunted to the emitter thereof, the series transistor T1 interrupts the current path for the thyristor Tyl, and the load resistor RL1 is disconnected from the subscriber line I. In addition the terminal point m3 of the holding circuit is driven by a pulse so that now the thyristor Ty2 ignites and forms a holding current (C2/R2), from part of which a base current is formed for the series transistor T3, which switches conductive so that the load resistor RL2 follows the rectifier bridge G12 in the subscriber loop (of II). This connection of the load resistor RL2 when the subscriber line II is cleared or when it is reconnected for a further conversation initiated via the cradle switch or the push-button block is effected by the actuation of the microprocessor M via t 10 the terminal point m4 of the holding circuit H2, in that the transistor Itf opto-coupler T4 becomes conductive, shunts the base current from ST3, and thus cuts off T3, and as a result the thyristor T2 is set I into the blocked state. Thus the load resistor RL2 is disconnected 0 0 from the subscriber line II (a2/b2).

It will be clear from the aforegoing that the holding 0 t 0 o, circuit in accordance with the invention can be controlled in a simple manner using switching means designed only for low current (push- 0 4 4 O buttons with rubber matrices), that it can be constructed from simple, integrable modules, and that no special structural outlay is required.

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Claims (3)

1. In a two-loop telephone supplied via a subscriber line, comprising a microprocessor control unit, a rectifier bridge for reverse polarity protection in the subscriber line, a push-button block for subscriber dialling, for emitting pulses to the microprocessor and special functions, and a requisite speech circuit including a change-over device for switching over from one subscriber line to another, wherein the microprocessor control unit controls connection and disconnection of a circuit path between wires forming the subscriber line in response to said impulses; an electronic holding circuit provided between the wires of the subscriber line, consisting of the series combination of a respective optically-driven thyristor, a load resistor and a series transistor, base current for the series transistor being branched from holding current of the associated thyristor, which has a respective transistor opto-coupler serving as switch 15 arranged in the base circuit, and both the thyristor and the transistor. opto-coupler in each case being connectable via a control line to control outputs of the microprocessor control unit for activation when the change- S over device switches from one subscriber line to another. S"

2. A two-loop telephone supplied via a subscriber line, comprising a microprocessor control unit, a rectifier bridge for reverse polarity protection in the subscriber line, a push-button block for subscriber o. dialling, for emitting pulses to the microprocessor and special functions, and a requisite speech circuit including a change-over device for switching oo° over from one subscriber line to another, wherein the microprocessor 25 control unit controls connection and disconnection of a current path between wires forming the subscriber line in response to said impulses; characterised by an electronic holding circuit provided between the wires of the subscriber line, consisting of the series combination of a respective optically-driven thyristor, a load resistor and a series *0O transistor, base current for the series transistor being branched from holding current of the associated thyristor, which has a respective transistor opto-coupler serving as switch arranged in the base circuit, and both the thyristor and the transistor opto-coupler in each case being connectable via a control line to control outputs of the microprocessor control unit for activation when the change-over device switches from one subscriber line to another. gr/280r

3. An electronic holding circuit substantially as described with reference to the drawing. DATED this NINETEENTH day of FEBRUARY 1990 Siemens Aktiengesellschaft Patent Attorneys for the Applicant SPRUSON FERGUSON 0 so4 -7 gr/280r