GB2064917A - Emergency telephone networks - Google Patents

Abstract

A method of checking the operability of line sections and the permanent availability of an emergency enquiry station NRA in which there are assigned to each of the emergency enquiry stations NRA special signal sources SA, each for generating a test signal which also conveys an indication of its own station, which periodically occupy the groups of lines between the switching centres VST associated with the stations NRA with checking operations. in a called emergency enquiry station NRA, an indicator effects the identification of the state of a line. Change-over of a local network area to guarantee availability is always initiated by the taking-over emergency enquiry station NRA, and permanently connected lines LT are provided between the switching centres VST for this purpose. <IMAGE>

Description

SPECIFICATION Emergency telephone networks The invention relates to emergency telephone networks, and is particularly concerned with checking lines or line sections thereof.

According to one aspect of the present invention, there is provided an emergency telephone network, comprising: a plurality of emergency enquiry stations for receiving emergency calls; a respective test signal generator assigned to each station and operative to generate a test signal conveying an indication of the respective generator; and testing means for transmitting a test signal from the generator of one said station to another said station at intervals, in order to test lines between the stations.

According to another aspect of the present invention, there is provided a method of testing lines between a plurality of emergency enquiry stations in an emergency telephone network, the method comprising the steps of generating a test signal in each of said stations, each test signal conveying an indication of its respective station, and transmitting said signals at intervals from one of said stations to another.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will be made, by way of example, to the accompanying diagrammatic drawing, which shows a block circuit diagram of an arrangement of several emergency enquiry stations in an emergency telephone network.

Emergency enquiry stations NRA have several enquiry points PL, which are each connected to a respective switching centre VST by a permanently assigned exchange line. To check the operability of the lines and the availability of emergency enquiry stations, there is assigned to each emergency en quiry station N RA a respective test signal generator or source SA with an indicating device. The signal sources SA are each coupled with a respective timer ZG, and are connected via an evaluating arrangement or analysing device AV to the exchange lines. At regular intervals of time, a checking operation (test) by a signal source SA is brought about.For example, a test connection may be made from an originating signal source SA2 to a called emergency enquiry station NRA1, which then occupies a line to one of the receivers assigned to each enquiry point PL of the called emergency enquiry station NRA1.

The test signals for checking the operability of the lines also convey identification of the source of the checking operation - in the example given, this would be identification of the emergency enquiry station NRA2. The checking operation is distinguished from normal communications signals in use by a special sign. A multi-frequency method is preferable for the sign transmission, whilst for the signal emission, for example, a loop-identification process, or other signalling processes are used. In a central indicating arrangement which, if necessary, is assigned to the signal source SA, local coordination is established by means of the identification process, and the source is indicated.No special branch line is provided for the checking operation; it uses any of the available connection lines between the switching centres VST and any exchange line assigned to the emergency enquiry stations NRA, in order to test their operability at fixed intervals of time. All lines of a group are thereby cyclically scanned.

If no connection is made for use within a predetermined length of time, then a checking operation is initiated from a pre-arranged, or, respectively, an originating switching centre by the signal source SA.

If no connection for use and no checking operation is made over a certain time, the original identification is cancelled. With the same periodic testing, availability is checked. There are assigned to the receivers operation displays, which indicate a state of disturbance if connection does not occur over a length of time determined by the time ZG.

Each emergency enquiry station NRA can also take over the emergency calls of other areas, as well as those calls of its own area. The availability of an emergency enquiry station is thereby guaranteed even if the emergency enquiry station of the local emergency call is not connected or disturbed, or if it does not receive a test signal transmitted to it. To this end, the switching centres VST are connected with each other via permanently connected branch lines, or, respectively, branch lines of a particular type LT, or, respectively, selector connections. The taking-over (re-routing) of an area, whereby the area assignments are determined in respect of the takenover calls, is always controlled by the taking-over station. The emergency call lines, e.g. NL3, are thereby disconnected from the exchange lines of the emergency enquiry station, e.g.NRA3, to be taken over, and connected, or respectively, directed on to the branch lines of a particular type, e.g. LT3. Directly after the take-ovel, a checking operation (line test) is initiated as acknowledgement, which also places the assigned originating display of the taken-over station in the taking-over emergency station, e.g. NRA1, to indicate visibly completion of take-over.

Cancelling the take-over calls is initiated by the emergency enquiry station which from this moment has the relevant local area to attend to. By these measures it is ensured, that in the vent of a deficiency in an emergency enquiry station, there is no need to initiate a diversion of the take-over calls to other enquiry stations. Since identification is given of a take-over in the other emergency enquiry stations by extinguishing the originating display, the emergency enquiry station, determined for take-over up to this point, can identify, as a result of this signal, the take-over of the other emergency enquiry station.

The take-over of the emergency calls of another local network area to guarantee availability is controlled in the following way. After the taking-over emergency enquiry station NRA has initiated permanent connection to the station, or, respectively, switching centre VST, to be taken over, it awaits the ready-to-dial sign on the side of the pre-arranged switching centre. When the ready-to-dial sign has been received, a certain frequency sign is sent and the area assignment is checked by means of another frequency sign. When the release is detected of the switching centre, in which is assigned the emergency enquiry station NRAto be taken over, a checking operation is initiated and visible displays are placed for the areas to be taken over.

Claims (17)

1. An emergency telephone network, comprising: a plurality of emergency enquiry stations for receiving emergency calls; a respective test signal generator assigned to each station and operative to generate a test signal conveying an indication of the respective generator; and testing means for transmitting a test signal from the generator of one said station to another said station at intervals, in order to test lines between the stations.

2. A network according to claim 1, further comprising re-routing means for automatically rerouting calls of a first said station to a second said station, in the event that said first station is in a predetermined condition.

3. A network according to claim 2, wherein, in the event of the calls of said first station being re-routed to said second station, the testing means of said second station is arranged to emit a test signal to said first station, as an acknowledgement of completion of the re-routing.

4. A network according to claim 2 or 3, wherein said condition is one in which said testing means indicates that said first station does not receive a said test signal when transmitted to it.

5. A network according to any preceding claim, wherein each test signal has characteristics different from that of normal communications signals to and from said stations.

6. A network according to any preceding claim, wherein said testing means is operative to test all lines between a respective pair of said stations in a test.

7. A network according to any preceding claim, wherein each said generator is connected with a respective timing means, and is connected via a respective analysing device to exchange lines per manently assigned to the respective said station.

8. A network according to claim 6 or to claims6 and 7, wherein said testing means is operative to test cyclically all of the lines in a group of lines between respective switching centres assigned to a respective pair of said stations, in a test.

9. A network according to claim 5, or to claims 6, 7 or 8 as appendant thereto, wherein said test signals are distinguished byfrequencyfrom normal communications signals to and from said stations.

10. A network according to any preceding claim, including means arranged to carry out a loop identification process during transmission of a said test signal in a test.

11. A network according to claim 2, orto any one of claims 3 to 10 as appendant thereto, wherein said second station is arranged to control re-routing of calls to said first station.

12. A network according to claim 2, or to any one of claims 3 to 11 as appendant thereto, wherein any two of said stations are capable of serving as said first and second stations.

13. A network according to claim 2 or to any one of claims 3 to 12 as appendant thereto, wherein permanently connected lines are provided between respective switching centres of said stations for re-routing calls from said first to said second station.

14. An emergency telephone networksubstantially as hereinbefore described with reference to the accompanying drawing.

15. A method of testing lines between a plurality of emergency enquiry stations in an emergency telephone network, the method comprising the steps of generating a test signal in each of said stations, each test signal conveying an indication of its respective station, and transmitting said signals at intervals from one of said stations to another.

16. A method according to claim 15, when applied to an emergency telephone network according to any one of claims 2 to 14.

17. A method in accordance with claim 15 and substantially as described herein.