AU608150B2 - Circuit arrangement for switching a switching device from normal switching operation to an emergency operation and conversely - Google Patents

Abstract

To provide the possibility for an external call connection in the event of a fault preventing normal switching operation (mains failure, severe software error), a preferred subscriber station (T1) is directly connected to a predetermined exchange line. If such subscriber stations are conducting external calls when a fault occurs, these are not released during the transition from normal switching operation to emergency operation or during the transition in the reverse order to this. If the exchange line (AL1) is occupied by its associated preferred subscriber station (T1) via the corresponding connector unit (AS), the time delay otherwise existing during the switch-over of the change-over unit (U) is cancelled. If this exchange line (AL1) is seized by another subscriber (Tn), the existing call connection is released by the delayed switch-over. If a call connection exists for a preferred subscriber station, a switching path is first built up to the relevant connector unit (AS) during the transition from emergency mode to normal switching operation and the speech path is prepared. It is only then that the exchange line is connected to this preparatory path by the connector unit (U). <IMAGE>

Description

6oa$ S F Ref: 90803 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: vr his doumcnt contains the amendments made under Section 49 and is correct for printing Class Int Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: Name and Address of Applicant: Siemens Aktiengesellschaft Wittelsbacherplatz 2 8000 Muenchen FEDERAL REPUBLIC OF GERMANY Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Address for Service: Complete Specification for the invention entitled: Circuit Arrangement for Switching a Switching Device from Normal Switching Operation to an Emergency Operation and Conversely The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3 ti i -L -L i. Z i. i- U 1~ .1 Abstract Circuit arrangement for switching a switching device from normal switching operation to emergency operation and conversely To provide the possibility for an external call connertion in the case of a fault (mains failure, grave software error) precluding normal switching operation, a preferred subscriber station (Tl) is directly connected to a predetermined exchange line. If external calls are made by such subscriber stations during the onset of a fault, these calls are not released during the transition from normal switching operation to emergency operation or o P* during transition in the reverse order. If the exchange Does line (ALl) is seized by its associated preferred subo00 scriber station (Tl) via the corresponding connecting unit the time delay during the switch-over of the S switch-over unit which normally exists, is cancelled. If this exchange line (AL1) is seized by another subscriber the existing call connection is released by the delayed switch-over. If a call connection exists 8° 9 for a preferred subscriber station, a switching path to the relevant connecting unit (AS) is first set up during transition from emergency operation to normal switching operation and the speech path is connected in a preparatory manner. It is only after that, that the exchange line is connected to this preparatory path by the connecting 004 unit (Figure) L--e Siemens Aktiengesellschaft Circuit arrangement for switching a switching device from normal switching operation to an emergency operation and conversely.

The invention relates to a circuit arrangement for switching a switching device, particularly a computercontrolled key telephone switching device from normal switching operation to emergency operation and conversely, in which arrangement, during the emergency operation caused by a fault which precludes normal switching operation, at least one predetermined preferred subscriber station can be directly coruected to a predetermined exchange line and in which arrangement the necessary feeding voltage for the subscriber station concerned 15 is supplied via this exchange line.

*00 Ceo o. So that, in the case of a mains failure or with grave 0 software errors in a switching device, the capability for an external call connection is maintained for at least oe oG Sone subscriber station connected to it, it is known to connect an exchange line directly to this predetermined subscriber station. During this exchange line switchover, however, a call connection existing during the C' transition from normal operation to emergency operation zis released for this subscriber station. If it is desired 25 to continue the call, the connection must therefore be completely re-established. The subscriber stations which are connected to an exchange line during emergency operation of the switching device can be arbitrarily defined, for example via an operating terminal, in a switching device designed to modern principles.

The present invention has the object of improving the exchange line switch-over, particularly to make the necessary switch-over subscriber-friendly.

This ois acnheved by the fact that the line w-es-ofthis predetermined exchanqe line can be connected to theI 1 ~i 1cill"*lr-rr~,uyL~a~rxr~ -2- In accordance with the present invention there is disclosed a circuit arrangement for switching a switching device from normal operation to emergency operation and conversely, wherein, during emergency operation caused by a fault which precludes normal operation, at least one predetermined preferred subscriber station can be directly connected to a predetermined exchange line in which the necessary feeding voltage for said preferred subscriber station is supplied via said predetermined exchange line, in which the line wires of said predetermined exchange line (AL1) can be connected to said preferred subscriber station said arrangement comprising a switching control unit supplying said subscriber station and intra-system connecting paths connecting said exchange line via a switch-over unit said switch-over unit having a first switch position and, a second *4*o switch position in which said exchange line is directly connected to audio Oo signal carrying wires (alO, blO) of the preferred subscriber station (T1), "615 and with the exception of an external call connection set up by the preferred oe subscriber station the switch-over from the first to the second switch o% position is delayed by at least a time interval providing for a normal o release process such that when a transition from emergency operation to o normal switching operation is to be effected, with a call connection existing for the preferred subscriber station (Tl) via the associated exchange line (ALl), first both a connecting path is set to a connecting unit (AS) 0oO allocated to the relevant exchange line and switching functions (nsi) which can occur in said connecting unit (AS) are carried out and then, whilst maintaining that connection, the switch-over from the second switch position 26 to the first switch position is effected.

0: If a call connection exists during the transition from normal switching operation to emergency operation for a preferred subscriber station which is 0oo therefore directly connected to the associated exchcn line in such a case, the delay in the switch-over existing for other subscribers is cancelled according to the invention. The switch-over occur, within such a short time that the connection is not released. If such a call connection exists for another subscriber station, the delay is effective as a result of which the connection is released so that the telephone privacy is maintained. If due to such a preferred subscriber station a call connection exists in the time in which the switching device resumes its normal switching operation, such a connection is also not released. This is because, according to the A, invention, an internal path is first set to the connecting i k/11220 t-j -3unit responsible for the exchange line concerned and only then is the switch-over effected without additional delay. After that, the call can be handled via the switching system without influencing the call connection.

A further development of the invention consists in that a particular one of several exchange lines is allocated to a preferred subscriber station by means of a corresponding definition in the customer data store for the preferred use with outgoing external call connections.

Furthermore, it is provided according to the invention that with an arriving connection request, first the call to the preferred subscriber station allocated to the relevant exchange line is transmitted and forwarding to another subscriber station is only effected with an 15 unsuccessful call.

00a0 0000 o. o According to a further development of the invention, the switch-over unit is simply formed by a corresponding contact combination of a change-over relay. To implement the delay, a circuit delaying the drop-out of the changeover relay, is activated for the change-over relay with 0oo each external call connection set-up by a non-preferred 0 °subscriber station as a particularly simple solution. If thus a call connection exists for another subscriber 0:0" station, the change-over relay drops out with delay as a 0000 result of which the call connection is then released in the conventional manner. This releasing can be effected, °r for example, by interrupting the line loop by means of a switching unit which is contained in an exchange circuit provided as connection unit.

In the text which follows, the invention is explained with reference to the figure. This shows in a simplified block diagram some functional units of a switching device VE to which the subscriber terminals T1...Tn are connected in the form of a star. The speech transmission is to occur in analog manner in the illustrative embodiment.

For connecting the terminals, a four-wire connecting line 4 is used which in each case consists of a speech wire pair a/b and a signalling wire pair c/d. In a switching system which is exclusively digital, the control connection and the useful-signal connection provided for transmitting the speech information could be implemented on a two-wire connection line in which case at least one useful-signal channel and one control channel could be implemented by means of a particular time slot for each terminal. The subscriber terminals TI...Tn are connected to the electronic switching device KN via a connecting unit AT which, among others, contains the call connection and the indication for the subscriber line loop. For the circuit ALl... ALx leading to a public exchange, this is in each case effected via an associated connecting unit AS. The 15 control tasks of the switching device Ve are handled by o000 the central control processor unit ZSt which is coupled to the said AT and AS units and the other system components such as, for example, the switching device KN, a 0 a" unit MZ used for forming the multi-frequency code signals S"o 20 and a unit HZ which is responsible for generating the o o call progress tones. Such a connection also exists between this control processor unit and a processing unit B Q 0 go Ve which is allocated to each signalling wire pair c/d and which contains a transmit section S and a receive section E. Including the processing unit Ve, a two-way information transmission can be carried out between the terminal and the control processor unit ZSt via the signal wires c/d. For example, the information o a0 transmitted from the control processor unit to a terminal 30 via the signalling wires can be transmitted by means of a binary voltage modulation and the information to be transmitted in the opposite direction can be transmitted by a binary current modulation. The latter can then be used for signalling the operation of individual keys TS performed at the respective terminal. This should be effected, for example, in conjunction with the control unit Pe, by means of the unit IR. The information bits occurring at the respective c/d signalling wires due to the voltage modulation provided in the opposite direction

~FI

5 are registered by the unit UD in conjunction with the control unit Pe. They can relate to, for example, adjustment information for optical display elements LF.

The speech information is transmitted via the respectve speech wire pair a/b. The speech circuit Sp is connected to these speech wires. In conjunction with the handset HA, it is used for processing the speech information transmitted and forms the circuit termination.

The central control processor unit ZSt has access to the data stored in the storage device SE. Among others, these relate to the entire system program stored in the store P and to the associated operating data contained in o. the main memory A. The customer data are stored in the o000 memory section KD. This includes, for example, the 0 015 abbreviated dialling numbers provided for the switching device and the access levels allocated to the individual So subscriber terminals. It also contains information on o which subscriber terminal is directly connected to an 0 0 exchange line AL in emergency operation. It can also be defined that, in the case of a connection request arrivo ing on a particular exchange line AL, for example AL1, this is first signalled to a particular subscriber terminal, for example the subscriber terminal Ti. In cases in which, when a call is waiting, the call connection required is then not accepted, at least one further subscriber station can then be called. The data contained in the customer data store KD can be configured, for o example, via the input keyboard of a terminal which can be defined as operating terminal.

In the case of failure of the voltage supply SV or in the case of grave software errors, operation changes from normal switching operation to emergency operation. In such a case, a previously determined subscriber terminal, for example the subscriber terminal T1, is directly connected to an exchange li-i permanently allocated to it, for example to the exchange line ALl. This is ef- ;i r I~-UJ- r 6 fected by means of the switch-over unit U which, in the illustrative embodiment, is implemented by the contacts llu and 21u, which exhibit a normally-open and a normally-closed position, of a change-over relay LU. One exchange line wire is in each case connected via the normally-closed position of the two contacts via the wirea all and bll bypassing the switching device directly to the speech wires alO and blO of the terminal Tl. It can be provided that each exchange line ALl...ALx is in each case associated with such a preferred terminal which is directly connected to this exchange line in the same manner via a switch-over unit U with the onset of emergency operation. In a borderline case, the number of preferred subscriber terminals for which such a connec- 15 tion to the exchange line is provided in emergency o operation, can therefore correspond to the number of 0 S 0° these exchange lines.

S00 oo o 0 o It is appropriate that call connections coming from o O0 ao these preferred subscriber terminals are preferably handled via the exchange line allocated to them. Thus, in set up this relevant connection via the associated line.

0 a The search algorithms for the other subscriber terminals start with other exchange lines in which case the ex- I 25 change line allocated to a preferred subscriber can then be seized as the last line or not at all.

00o4 I o If a connection exists via the exchange line, for example via exchange line AL1 in normal operation, the change-over relay LU is set by the control processor unit ZSt. The associated contacts llu and 21u are therefore in a position in which the normally-open contact side is in the closed condition in contrast to the representation in the figure. The call is thus handled via the switching device. If the connection comes from a preferred terminal, for example from terminal Tl, the control processor unit ZSt also sets the relay VA so that the associated contact va is in the normally-open position. Thus, the i 7 delay section Vz causing a drop-out delay for the relay LU is thus deactivated. Thus, a drop-out delay for the change-over relay LU is cancelled. During a transition from normal operation to emergency operation, the exchange line is now switched over without additional delay since the re'lay LU drops out in such a case. The switchover occurs within such a short time that an existing call connection is not released. The call connection thus remains established due to the normally-closed position of the contacts llu and 21u thus assumed, bypassing the switching system via wires all and bll. If another subscriber Tn had seized the exchange circuit AS allocated to the exchange line AL1, the delay circuit Vz is active due to the contact va assuming its normally-closed o- 15 position so that the change-over relay LU drops out with a delay. Before that, the relay HSI, not shown, the contact E as

B

nsi of which is located in the exchange line circuit oeB- blocked off with respect to the switching array by a SO transformer Ue, has dropped out. This initiates the usual 20 release processes. Thus, whenever the connection has not been set up via a preferred terminal, the exchange connection is opened during transition from normal Bo." S operation to emergency operation and the switch-over to 0o the associated preferred terminal Tl is effected only then after the delayed drop-out of the relay LU. If a call connection exists for a preferred terminal Tl at the time at which the switching device changes back from emergency operation to its normal switching operation, ,sa this is detected in the initializing phase of the switch- 30 ing device. A switching path is then set up to the exchange circuit AS and the speech wire path in the exchange circuit is connected in a preparatory manner by operating the contact nsi. If this path has been set, the change-over relay LU is set by the central control processor unit ZSt. With, the corresponding operation of Sthe contacts llu and 21u, the call connection is switched over without any particular interfering influence and is thus handled via the switching device. If thus calls are made from the preferred terminals, these are not released .i L i -8during the transition from normal operation to emergency operation and during transition in the reverse direction.

6 Patent Claims 1 Figure 0 000~ 00 so 0 04 a0 b

Claims (9)

1. A circuit arrangement for switching a switching device from normal operation to emergency operation and conversely, wherein, during emergency operation caused by a fault which precludes normal operation, at least one predetermined preferred subscriber station can be directly connected to a predetermined exchange line in which the necessary feeding voltage for said preferred subscriber station is supplied via said predetermined exchange line, in which the line wires of said predetermined exchange line (ALl) can be connected to said preferred subscriber station said arrangement comprising a switching control unit supplying said subscriber station and intra-system connecting paths connecting said exchange line via a switch-over unit said switch-over unit having a S e first switch position and, a second switch position in which said exchange o line is directly connected to audio signal carrying wires (alO, blO) of the preferred subscriber station and with the exception of an external oC000 I, call connection set up by the preferred subscriber station the 0 0 switch-over from the first to the second switch position is delayed by at 0 least a time interval providing for a normal release process such that when 00 00 0 B a transition from emergency operation to normal switching operation is to be effected, with a call connection existing for the preferred subscriber station (TI) via the associated exchange line (ALl), first both a a connecting path is set to a connecting unit (AS) allocated to the relevant exchange line and switching functions (nsi) which can occur in said connecting unit (AS) are carried out and then, whilst maintaining that *o 00 o connection, the switch-over from the second switch position to the first switch position is effected. 0 0

2. An arrangement as claimed in claim 1 wherein said switching 0 oo, device is a computer-controlled key telephone switching device.

3. An arrangement as claimed in claim 2, wherein one particular o 4 exchange line (AL1) of several exchange lines (ALI...ALx) is allocated to a preferred subscriber station (TI) by means of a pre-programmed instruction in a customer data store (KD) for preferred use with outgoing external call connections. rhk/1122o r- 10

4. An arrangement as claimed in claim 1, 2 or 3, wherein for the case of a connection request arriving via an exchange line (ALl), first the call to the preferred subscriber station (Tl) allocated to the relevant exchange line (ALl) is transmitted and forwarding to another subscriber station is only effected with an unsuccessful call.

An arrangement as claimed in any one of the preceding claims, wherein the switch-over unit is formed by corresponding contact combinations (11u, 21u) or a change-over relay (LU).

6. An arrangement as claimed in claim 5 wherein said switch-over unit comprises normally-open contact sides llu and 21u for said first switch position and normally-closed contacts llu and 21u, for said second switch position. 0 r 0 o

7. An arrangement as claimed in claim 5, wherein with each external call connection set up by a non-preferred subscriber station a circuit (VZ) delaying the drop out of the change-over relay (LU) is o activated for the change-over relay (LU). 0o a 0

8. An arrangement as claimed in any one of the preceding claims, 0 0 wherein an exchange circuit (AS) is provided as connecting unit which, for releasing a connection, contains a switching unit (nsi) which makes it possible to interrupt the line loop.

9. A circuit arrangement substantially as described herein with reference to the drawing. DATED this EIGHTEENTH day of DECEMBER 1990 0Q 0 0 4 SSiemens Aktiengesellschaft 0 40 0 00 Patent Attorneys for the Applicant SPRUSON FERGUSON 71 U Pa' o; /11220 11 Y- II