GB2318257A

GB2318257A - Subscriber Interface of a Key Telephone System

Info

Publication number: GB2318257A
Application number: GB9721112A
Authority: GB
Inventors: Yong-Soon Moon
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1996-10-08
Filing date: 1997-10-07
Publication date: 1998-04-15
Anticipated expiration: 2017-10-07
Also published as: KR19980026208A; KR100407335B1; GB9721112D0; GB2318257B

Abstract

A radiotelephone subscriber interface of a key telephone system for interfacing data communications between the key telephone system and a plurality of base stations comprises respective sync signal generators and transceivers corresponding to the base stations. The sync signal generators generate the sync signals of respective base stations. The transceivers transmit control data and sync signals through their respective channels. The base stations extract radio sync signals from the respective sync signals received through corresponding channels.

Description

SUBSCRIBER INTERFACE AND METHOD OF A KEY TELEPHONE SYSTEM Background of the Invention The present invention relates to a subscriber interface of a key telephone system.

Generally, key telephone systems employ multi function cards as system modules. In such multifunction or option cards, the shared signal line and control data lines are connected to the key telephone system through the platform bus. The platform bus includes address, data, and control buses, and a highway carrying audio data and clock signals.

One such option cards is a digital line interface ("DLI") card. In the application of DLI to the digital key telephone system, a digital key subset is used and is connecting via the transceiver of the DLI. Various applications may be implemented by connecting the telephone and/or data terminal modules to the digital key telephone system by means of the transceiver of the DLI.

Fig. 1 illustrates an application of a DLI to a key telephone system. The Single Line Interface (SLI) ) Card shown is a subscriber card which servs analog subscribers.

A radio telephone set can be connected to the SLI in the method of general telephone connection, and operated in parallel with the general telephone sets. That is, even when large numbers of radio telephone sets are used, individual sets can be controlled like general telephone sets, without the need for a separate control signal allocated by the key telephone system.

In Europe, the European Telephone Standard Institute (ETSI) has proposed a digital cordless telephone standard at the European level, i.e., the Digital European Cordless Telecommunication system (DECT). It is forecast that this DECT standard will be soon adopted in the Republic of Korea. Accordingly, when commercially connecting the remote radio terminals of the DECT standard to the key telephone system, the conventional key telephone system must be able to provide the following functions.

Firstly, when connecting a plurality of DECT base stations ("DBS") to the key telephone system, the key telephone system should be able to generate synchronizing signals, so that each of the DBSs can communicate based on time division multiple access ("TDMA"). Secondly, the system should be able to accommodate a plurality of option cards.

That is, if the platform bus does not allocate a separate signal line to provide a commonly needed signal, the option card should generate the signal for itself. Thirdly, when connecting a plurality of DBS modules, a connecting method between the key telephone system and the DBS should be provided, including methods for power supply, audio and data transmission, and synchronizing signal transmission, etc.

Summary of the Invention Accordingly, it is an object of the present invention to provide a device and method for interfacing the radio telephone subscribers with the key telephone system.

According to the present invention, a radiotelephone system comprises: a key telephone system; and a plurality of base stations; in which the key telephone system includes a subscriber interface for interfacing data communications between the key telephone system and the plurality of base stations, the subscriber interface comprising a plurality of sync signal generators for generating sync signals for respective base stations and a plurality of transceivers for transmitting control data and the respective sync signals via their respective channels; and in which the base stations are adapted to extract their respective sync signals received via corresponding channels so as to transmit radio data.

Preferably, the sync signal generators are adapted to count frame sync signals after the transition to a normal state of a system initializing signal, thereby to generate the respective sync signals.

The present invention also provides a method of operation of a radiotelephone system comprising a key telephone system and a plurality of base stations, the method comprising: in a subscriber interface of the key telephone system, generating sync signals for the respective base stations and transmitting control data and the respective sync signals via respective channels; and in the respective base stations, extracting their respective sync signals received via corresponding channels by which to transmit radio data.

Brief Description of the Drawings The present invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 shows the general architecture of a key telephone system connected to subscriber telephone sets; Fig. 2 is a block diagram illustrating the key telephone system connected with radiotelephone subscribers according to the present invention; Fig. 3 is a block diagram of the subscriber interface shown in Fig. 2; Fig. 4 illustrates the constituent elements of the clock generator shown in Fig. 3; Fig. 5 is a timing chart illustrating the synchronizing signals between the key telephone system and the radiotelephone subscribers in the system as shown in Fig. 2; and Fig. 6 illustrates the constituent elements of the synchronizing signal generator of the radiotelephone subscribers.

Detalled Description of the Preferred Embodiment Referring to Fig. 2, the key telephone system comprises a plurality of base station interfaces ("BSI") BSIl-BSIm, by which each BSI is connected with a plurality of base stations DBS1-DBSn to serve as an interface between the key telephone system and the radio terminals.

Fig. 3 illustrates the constituent elements of BSIl-BSIm.

A serial-parallel converter 301 interfaces the address and data transmission between the control unit of the key telephone system and the BSIs. The dual port RAM (DPRAM) 315 is a memory to be accessed independently by both the key telephone system and the processor 311 of the BSI. The processor 311 controls the overall operations of BSI. The ROM 312 is a memory storing BSI control programs of the processor 311. RAM 313 is a memory temporarily storing data produced during the program execution of the processor 311.

The oscillator 314 generates clock pulses to synchronize the operation of the processor 311. The clock generator 317 generates the clock signals of the processor 311 and the digital adapter for subscriber loop ("DASL").

Fig. 4 illustrates the constituent elements of the clock generator 317. The clock generator counts frame synchronizing signals FSX to produce first and second clock signals when the initializing/reset signal undergoes a transition to a normal state, by which the clock generator 317 generates a second clock signal of 80ms to apply to the processor 311 and a first clock signal of lOms to apply to the DASLs. The DASLs are connected with DBSs and serve as interfaces between the DBS and the key telephone system.

Assuming that each DBS is connected with two DASLs, and each BSI serves four DBSs, thus each BSI is connected with eight DASLs 1-8. The digital module controller 318 connects between the processor 311 and the DASLs 1-8, thus controlling the interface operations of the DASLs 1-8. As the DASLs 1-8, the commercially available TP3043 may be used, manufactured by the National Semiconductor Company.

The universal asynchronous receiver & transmitter driver ("UART") 316 forms a data path between the BSI and the external devices. The UART 316 may be connected with measuring instrument devices.

As described above, the BSI of Fig. 3 includes a digital module controller ("DMC") 318 connected with a transformer (not shown in the drawings) supplying power to a plurality of DBS modules (four DBSs 1-4 in the embodiment described).

DASLs 1-8 of ping-pong type transceivers are controlled by the DMC and a clock generator 317 generates synchronizing signals by means of a frame synchronizing signal and the initial/reset signal. The BSI further comprises DPRAM 315, processor 311, ROM 312, and RAM 313, in order to perform inter-processor communication (IPC) between the key telephone system and the BSIs.

Fig. 5 illustrates the timing of the synchronizing signals used by the respective DBSs, in which it is assumed that four DBSs are served by each BSI and each of DBSs 1-4 produces at the time of data interfacing their respective synchronizing signals. Fig. 6 illustrates the regeneration of the synchronizing signal received by DBSs 1-4.

The following explains the interfacing operation according to the present invention with reference to Figs. 2-6. The key telephone system generates a common signal for activating the highway, transferring audio and data signals. The BSI receives the frame synchronizing signal FSx indicating the beginning of availability of the highway, and the bit clock BCLK distinguishes each bit for the next. The above signals are applied to all the boards, enabling any other card to transfer audio and data signals.

Then the clock generator 317 as shown in Fig. 3 generates a first clock signal lOms and a second clock signal 800ms required for DECT by using the frame synchronizing signal FSx. The clock generator 317 generates lOms and 800ms on the platform bus by using the reset signal for initializing the frame synchronizing signal FSx and all the cards. That is, the clock generator 317 begins to count the Fsx after the reset signal becomes normal, generating 10ms and 800ms signals required for DECT. As mentioned above, the synchronizing signals are generated at the same time within a plurality of BSI boards.

In the embodiment of the present invention, the BSI board connects the DBS modules by a four-wire method, whereby two TCM transceivers are connected to one DBS. The transceivers are DASLs 1-8. Since the transceivers each have a transmission capacity of 2B+D, each DBS can interface communications between four radio subscribers at the same time. For example, when four DBSs can be connected within a BSI, they constitute a DECT system having a multi-cell structure as shown in Fig. 2.

In the above configuration, one of two transceivers transfers the control data, and another one transfers the synchronizing signal. In the ping-pong type transceiver, the B-channel for transferring audio data and the D-channel for transferring control data may not be synchronized, which is the case when the data are output with random timing when the timings of the B- and D-channels are transferred in opposite directions. When the above transceiver uses DASL, the above situation can arise. That is, when the BSI transfers a certain synchronizing signal to all the DBSs through a single D-channel, even at the same time, the synchronizing signals produced by each of the DBSs are different from each other, they thus being impossible to use as synchronizing signals.

Gating signals are generated to activate the DBSs, thus enabling data transfer by sampling data signals as clock pulses like BCLK received. In this case, the synchronizing signals transferred from the BSI are included in the same frame as shown under reference numerals 511-513 of Fig. 5.

Also in this case, the synchronizing signals of D-channel generated by each of the above DBSs are not consistent with each other as shown under reference numerals 522 and 524 of Fig. 5.

Accordingly, in order to extract the above synchronizing signals, the above DBSs 1-4 are each provided with the respective sync signal extracting circuits as shown in Fig.

6. That is, the above sync signal extract circuit as depicted in Fig. 6 receives the B-channel sync signal Fsc, as clock pulse, thereby generating RFSYNC synchronized with Fsc, and being used as synchronizing signal by each of DBSs 1-4. The above B-channel sync signal Fsc is affected by the distance between BSI and DBS to be changed. As illustrated in Fig. 5, the difference of the B-channel sync signal Fsc between each of DBSs is represented as FSdiff, and the difference of the sync signal SYNC transferred through D-channel is represented as SYNCdiff. Besides, the sync signals RESYNC adjusted by the above sync signal extracting circuit are represented as RFSYNC1 and RFSYNC2 as shown under reference numerals 525 and 526 in Fig. 5.

According to the DECT standard, the interval of the above synchronizing signals RESYNC shall be within 4ps. The digital module controller 318 of the BSI is a dedicated integrated circuit connected between the processor 311 and the transceivers DASL 1-8, performing the data sending/receiving operations through D-channel and generating control signals required for the transceivers.

As explained above, the present invention has the advantage that the radio telephone set of the DECT standard currently adopted in Europe can be applied to a key telephone system, which can further provide the handover and roaming functions, optimizing the mobility of the radio telephone and improving the call processing service by minimizing the probable call missing.

Claims

1. A radiotelephone system comprising: a key telephone system; and a plurality of base stations; in which the key telephone system includes a subscriber interface for interfacing data communications between the key telephone system and the plurality of base stations, the subscriber interface comprising a plurality of sync signal generators for generating sync signals for respective base stations and a plurality of transceivers for transmitting control data and the respective sync signals via their respective channels; and in which the base stations are adapted to extract their respective sync signals received via corresponding channels so as to transmit radio data.

2. A radiotelephone system according to claim 1, in which the sync signal generators are adapted to count frame sync signals after the transition to a normal state of a system initializing signal, thereby to generate the respective sync signals.

3. A method of operation of a radiotelephone system comprising a key telephone system and a plurality of base stations, the method comprising: in a subscriber interface of the key telephone system, generating sync signals for the respective base stations and transmitting control data and the respective sync signals via respective channels; and in the respective base stations, extracting their respective sync signals received via corresponding channels by which to transmit radio data.

4. A radiotelephone system substantially as described with reference to and/or as illustrated in Figs. 2 et seq.

of the accompanying drawings.

5. A method of operation of a radiotelephone system substantially as described with reference to and/or as illustrated in Figs. 2 et seq. of the accompanying drawings.