GB2177244A - Paging system - Google Patents

Abstract

An on-site paging system comprises a local transmitter 12 for transmitting local paging signals at a first frequency over a limited range to local paging receivers 20 such that each receiver 20 responds to its individual address. An external transmission receiver 16 receives area wide transmissions at a second frequency (which is different to the first frequency). The local transmitter 20 is responsive to a control terminal 11 to re-transmit at the first frequency the received external transmissions such that the paging receivers 20 can receive both the local paging signals and area wide paging signals. <IMAGE>

Description

SPECIFICATION Paging system The present invention relates to a paging system, and in particular to such a system which enables paging calls emanating from two separate sources and transmitted on two different frequency channels to be received by a single paging receiver operating on only one of those frequency channels.

Wide area paging systems are now prevalent in which a central organisation, such as British Telecom in the United Kingdom, provides transmissions composed of message signals intended for specific paging receivers which respond to the particular received message signals to provide an alarm tone, display or the like. These transmissions are broadcast over wide areas so that the message signals can be received relatively independently of the specific geographical location of the paging receiver at the time that the particular message signal is broadcast. Most developed countries now have such country-wide or city-wide paging systems working on dedicated frequencies.

All large systems now use digital codes to select specific receivers, the circuits of which include battery economy arrangements which require a preamble to be sent out before transmission of individual calls to receivers.

Thus the transmission system is arranged to store all calls to be sent out, and then to transmit the messages in batches preceded by the preamble.

In addition to these wide area systems, there are also on-site systems available, in which the purpose is to transmit message signals over much shorter distances than in wide area systems, it generally being sufficient to provide coverage over a single building or group of buildings, such as in a hospital.

Wide area systems usually operate at very high frequency (VHF) or ultra high frequency (UHF) whereas on-site systems generally utilise high frequencies (HF). Previously, if an individual required both wide-area and on-site paging facilities, it was necessary to carry two separate paging receivers.

According to the invention there is provided an on-site paging system comprising a local transmitter for transmitting local paging signals at a first frequency over a limited range to paging receivers such that each particular receiver responds to its individual paging signal, and an external transmission receiver arranged to receive external transmissions at a second frequency different to the first frequency, the local transmitter being operative to re-transmit the received external transmissions at the first frequency such that the paging receivers can receive both the local paging signals and paging signals carried by the external transmissions.

In a preferred arrangement, a control terminal is provided which, as one function, encodes the paging signal and supplies it to the local low power transmitter. The paging receivers operate within the limited range of the local transmitter. At this same location is also situated the external transmission receiver, tuned to the wide area paging frequency; all wide area calls received are passed to a buffer store in the control terminal.

The invention will now be described, by way of example, with reference to the accompanying single figure drawing which shows a block diagram of one embodiment of a paging system according to the invention.

Referring to the drawing, an on-site paging system 10 includes a control terminal 11 arranged to encode local paging signals and supply these signals to a local transmitter 12.

For this purpose, the control terminal 11 includes a local encoder and controller 13 responsive to one or both of an operator keyboard 14 and telephone access 15. An external transmission receiver 16, tuned to the wide area paging frequency, is arranged to pass all received wide area calls to a buffer store 17 in the control terminal 11. The address section of each incoming call (that part of the digital code used to identify the particular paging receiver for which the call is intended) is then compared in a comparator 18 with a number of wide area addresses already held in another store 19 in the control terminal 11. The addresses in this store 19 are those of people who have wide area paging receivers but who wish to carry only their onsite receivers 20, whilst in the immediate vicinity of that site.

The addresses are entered into the control terminal 11, as individuals come on to the premises and replace their wide area receivers by their on-site receivers. The wide area address and on-site address, for each person, is linked within the address store 19. When the address of an incoming wide area paging call matches one of the entries in the address store 19, then the control terminal 11 will initiate a local call to the associated on-site paging receiver 20.

Paging codes and receivers are designed so that the latter can emit a variety of different sound alert (bleep) patterns; the CCIR standard Radio Code No 1 (4 alert patterns) and the Multitone Digital Paging Code (8 alert patterns) are examples. If one pattern is designated to paging calls originating from the wide area system and a different pattern designated for local calls, the user knows which type is being received. The receiver could equally well be equipped with 2 lamps which would indicate the source of the call. Both wide area and on-site systems, currently in use, employ different alert patterns to indicate the source or type of paging call, thus if 4 patterns are available in the on-site receiver, 2 can be allocated to wide area calls and 2 to local calls.

There is a possibility that a wide area call for a particular user enters the control terminal 11 at the same time as a local call is initiated; the order in which they are transmitted will depend on which is processed first. If the design of the on-site paging receiver is such that it does not store the second call until the alert pattern of the first call has emitted its full cycle of bleeps, then it may be necessary to store the second call in the control terminal 11 for the appropriate period of time. Where the receiver can store the second call and give two alert patterns in sequence, then the control terminal 11 can pass the second call to the transmitter 12 immediately after the first.

In some on-site operations, eg, a hospital, there may be situations where a local call, immediately following a wide area call, cannot be allowed to wait for the time taken by the complete wide area alert pattern. The paging receiver can be designed so that when its decoder recognises the data bits corresponding to the alert pattern of the second (local) call, this is immediately allowed to override the wide area alert pattern. Obviously the wide area alert pattern is not allowed to override the local alert pattern if the calls are received in reverse order.

The wide area addresses can be entered into the control terminal 11 through the keyboard 14 by, say, the telephone operator or receptionist, but a better method is to employ storage/absence racks 21. In conventional onsite systems, these racks 21 are wired to the control terminal 11, so that if an individual has not reported for work, and his/her paging receiver remains in the rack, then anyone paging that person is immediately and automatically informed that they are absent.

It is possible to design the system such that when an individual carrying a wide area paging receiver reports for work, they take their local paging receiver 20 out of the rack 21 and wear this instead of the wide area paging receiver which is now put into the rack 21. The rack 21 detects that this is a wide area pager and automatically enters its address into the address store 19.

Where the wide area paging receiver is capable of displaying numeric or alpha-numeric information, which cannot be transferred to the local paging receiver because it has limited, or perhaps no display facility, then the display information would be printed out by the control terminal and an appropriate "display information available" tone alert pattern would be emitted by the local paging receiver.

Claims (14)

1. An on-site paging system comprising a local transmitter for transmitting local paging signals at a first frequency over a limited range to paging receivers such that each particular receiver responds to its individual paging signal, and an external transmission receiver arranged to receive external transmissions at a second frequency different to the first frequency, the local transmitter being operative to re-transmit the received external transmissions at the first frequency such that the paging receivers can receive both the local paging signals and paging signals carried by the external transmissions.

2. A system according to claim 1, wherein a control terminal is provided for encoding the local paging signals and for supplying the signals to the local transmitter.

3. A system according to claim 2, including a buffer store provided in the control terminal, the buffer store being arranged to store the received external transmissions prior to retransmission by the local transmitter.

4. A system according to claim 2 or claim 3, wherein the control terminal comprises a wide area address store in which is stored a plurality of wide area addresses which may be carried by the external transmissions, and an address comparator for comparing the received external transmissions with the addresses in the wide area address store.

5. A system according to claim 4, wherein the local transmitter is responsive to a positive comparison made by the address comparator to retransmit the particular received external transmission.

6. A system according to claim 5, wherein the local transmitter retransmits the particular received external transmission with the addition of a specific local address.

7. A system according to any one of the preceding claims, wherein the paging receivers each comprise means for distinguishing whether a received paging signal is local or external in origin.

8. A system according to claim 7, wherein the distinguishing means comprises a sound alert producing means arranged to provide audibly distinct alerts depending on the origin of the received paging signal.

9. A system according to claim 7, wherein the distinguishing means comprises two lamps, illumination of which depends on the origin of the received paging signal.

10. A system according to any one of the preceding claims, wherein each paging receiver comprises means responsive to a predetermined pattern of data in the received local signal to override a wide area alert pattern in a re-transmitted external transmission.

11. A system according to any one of the preceding claims, comprising a storage/absence rack arranged to store the paging receivers and to provide control signals dependent on whether particular paging receivers are present in the rack or not, such that an indication is provided by the control signals if a local transmission is made for a paging receiver which is still in the rack.

12. A system according to claim 11, wherein the storage/absence rack is arranged to store both the paging receivers for local use and also wide area paging receivers, whether a particular received external transmission is re-transmitted locally depending on the control signals from the rack.

13. A system according to any one of the preceding claims, comprising display means for displaying numeric or alphanumeric information provided in the received external transmissions, and means for transmitting locally a "display information available" signal to the respective paging receiver.

14. An on-site paging system substantially as herein described with reference to the accompanying drawing.