SWITCHING SYSTEM

Abstract: Switching system, comprising an exchange (1) and a number of subscriber stations (2), connected to said exchange through a cable network (7). Each subscriber station comprises selecting means (21) for generating selecting signals for selecting one out of a number of program or data signals available in the exchange, which selecting signals are stored into a buffer register (22) in each subscriber station. The exchange comprises scanning means (11) for sequencially transferring scanning signals to said buffer registers. The buffer registers are activated by said scanning signals to transmit the therein stored signals to the exchange. The exchange furthermore comprises control means (10, 15) for deriving control signals from the received selecting read out of said buffer registers for controlling switching means (3) in the exchange such that the program or data signals selected by means of the selecting signals are transferred from the exchange through the cable network to the subscriber concerned.

Description: Switching system. The invention relates to a switching system, comprising an ex¬ change and subscriber stations connected to said exchange through a cable network, whereby each subscriber station comprises selecting means for generating selecting signals for selecting one out of a number of program or data signals available in the exchange, which selecting signals are stored into a buffer register, and the exchange comprises scanning means for scanning the buffer registers and control means for deriving control signals from the selecting signals read out of said buffer registers fopr controlling switching means in the exchange such that the program or data signals selected by means of the selecting signals are transferred from the exchange through the cable network to the subscriber concerned. Such a switching system is already known and can be used for transferring television signals from an exchange to televsion re- ceivers, installed in the connected subscriber stations. However, such systems can also be used for transferring radio signals, data signals etc. In the following special reference will be made to a system for selecting television signals. Each of the subscribers in a television system has selecting means, for instance in the form of a key board, ,by means of which one out of n television programs can be selected. The selecting signals generated by said selecting means are transferred -over- the- cable network to the exchange and are there stored in a buffer register. Scanning means in the exchange are sequencially scanning all the buffer registers. The read out selecting signals are supplied to control means for deriving control signals from these selecting signals for controlling switching means in the exchange such, that the program selected by a subscriber is transferred to said sub¬ scriber. Said switching means comprise for each subscriber in prin- ciple n in general electronic switches, each with the input connected to one out of n program signal bus lines, whereby the outputs are pa¬ rallel connected to the concerned subscriber output. Under the in¬ fluence of the control signals one out of this group of n switches is closed, so that a connection is realized between one of these program signal bus lines and the subscriber output. OMPΪ The object of the invention is now to change the configuration of a switching system of this type such, that the possibilities of the switching system are significantly increased. According to the invention said object is in a switching system of the above mentioned type achieved in that said buffer registers for the selecting signals are positioned into the subscriber stations, the scanning means are sequencially transferring scanning signals via the cable network to each of the subscriber stations, and the buffer registers are activated by said scanning signals to transmit the therein stored signals. In the prior art switching system the subscriber stations would transmit selecting signals on their own initiative to the exchange asynchronously with the operation of the scanning means. In the switching system according to the underlying application however the subscriber station are passive and the selecting signals generated by the selecting means in each subscriber station are stored into a buffer register which is located in the subscriber station itself. The selecting signals are transferred to the exchange only after the scanning means have transmitted a scanning signal from the exchange to the buffer register in the subscribdr station. Only then the buffer register is activated to transmit the stored information through the cable network to the exchange. In this configuration according to the invention furthermore all the cable connections between the subscriberstations and the exchange are continuously tested. The fact that after transmitting the scanning signals from the scanning means over the cable network to the subscriber stations the contents of the buffer register of said subscriber station is transmitted over the cable network to the exchange indicates, that the concerned cable connection between the exchange and this scanned subscriber station is not interrupted and that the buffer register in the concerned subscriber station reacts onto the received scanning signals by transmitting his contents to the exchange. If the exchange does not receive any response onto a transmitted scanning signal, that will be an indication that there is a fault in the cable connection and/or in the bufferregister. In said buffer registers for instance digital shift registers can be used which after reception of a scanning signal transmit the - XJR£ _ _ OMPI yty ? , IPO stored information in a serial form. If necessary the digital output signals can be modulated in a modulator between the buffer register and the subscriber terminal. In a preferred embodiment of the switching system a special code is stored into the buffer register during or after transmission of the input of said buffer register to the exchange. When the inform¬ ation is shifted out of said digital shift register then it is pos¬ sible to fill such a register with zeros. If the subscriber there¬ after does not select any new program, then the buffer register will, after receiving the next scanning signal transmit said series of zeros to the exchange. The reception of a " series of zeros in the exchange indicates, that still the same program should be transmited to the concerned subscriber. In that case it is not necessary to take any further action in the exchange. Because of the proposed configuration of the switching system it is furthermore possible not only to transmit selecting signals for selecting television programs, but also signals derived for instance from an aged people alarm installation, a fire alarm installation, a burglar alarm installation, signals derived from a special input unit, for instance for view data applications etc, and also other types of data signals. These signals of different types, which are not destined for selecting television programs, are in the following indicated as condition signals or data signals. A preferred embodiment of the switching system according to the invention is characterized in that in stead of selecting signals also condition signals or data signals which arew not related to program selection can be stored into the buffer registers,which condition or data signals can be transferred to the exchange in the same as the selecting signals, whereby the exchange comprises means for distin- guishing between said selecting signals and the condition signals or data signals. Further features and advantages of the invention will be clearly explained in the following detailed description of a preferred embo¬ diment of the switching system according to the invention. Fig. 1 illustates a principle schematic diagram of a switching system according to the invention. The switching system illustrated in Fig. 1 comprises an exchange O PI 1 to which a number of subscriber stations is connected of which in the figure only two stations are illustrated, the subscriber stations 2a and 2m. The subscriber stations 2a... 2m are connected to the exchange 1 through cable connections 7a... 7m. 5 In the exchange 1 all the available program signals are supplied through signal inputs 4a, 4b... 4n to bus lines 5a, 5b... 5n. For each of the connected subscribers the exchange 1 comprises switching means 3a... 3m by means of which a connection can be realized between one of said bus lines 5a, 5b... 5n and the related subscriber output 10 6a... 6m of the exchange. Said switching means contain in principle n switches of which one* at a time can be closed. Therefore said switching means 3a can be used for realizing a connection between one of the lines 5a... 5n and the subscriber output 6a, and the switching means 3m can be used for realizing a connection between one of the 15 bus lines 5a... 5n and the subscriber output 6m. Each of the subscriber stations contains a television receiver 20a, 20m connected to the subscriber terminal 23a, 23m, and further¬ more selecting means 21a, 21m which through buffer registers 22a,22m are also connected to the subscriber terminal 23a, 23m. In the figure 20 the television receivers 20a, 20m and the buffer registers -22a, 22m are connected to said subscriber terminal 23a, 23m through a separ¬ ation filter 27a, 27m. However, this separation filter is not neces¬ sary under all circumstances. Furthermore in the exchange 1 a control unit is installed, which 25 is through the lines 12a... 12m coupled to the respective switching means 3a... 3m and functions for controlling said switching means. Also a scanning unit 11 Is installed in the exchange 1 connected through the lines 13a... 13m and the separation filters 14a... 14m to the subscriber outputs 6a... 6m of the exchange 1. The control unit 30 10 as well as the scanning unit 11 are coupled to a processor 15. Now the operation of this switching system will be described with special reference to the subscriber station 2a. However, it will be clear that the operation is identical for all subscriber stations 2a... 2m. The components 24a.... 24m, 25m, 26m, will for the time 35 being left out of consideration and will be discussed later. In the subscriber stations 2a selecting signals are generated by operating the selecting means 21a, which selecting signals for instance in the form of a number of digital bits are stored into the buffer register 22a. The scanning unit 11 in the exchange 1 is con- trolled by the processor 15 such that the scanning unit is transmit ¬ ting sequentially scanning signals to each of the subscriber stations 2a... 2m. At the reception of these scanning signals the buffer re¬ gister 22a is activated to transmit the stored contents. The scanning signals may comprise for instance a number of shift pulses, by means of which the contents is shifted out of the buffer register 22a, but they can also comprise a start pulse for activating a generator coupled to the buffer register 22a to generate a number of shift pulses. The Information transmitted by said buffer register 22a is, whether or not after modulation, transferred via the cable connection 7a to the exchange 1 and is via the subscriber output.6a, the separ¬ ation filter 14a and the line 13a received by the scanning unit 11. The processor 15 supplies these received signals, eventually after a conversion process to the control unit 10, which generates control signals over the line 12a for controlling the switching means 3a such, that these switching means 3a are transferring the program, which was selected In the subscriber station 2a from the bus line 5a... 5m to the subscriber output 6a. Via the cable connection 7a and the separation filter 27a the selected program signal is received by the television set 20a. The buffer register 22a can be embodied such that during read out operations the information is shifted back to the input so that the information will be contained, but preferably a shift register is used which is during a read out operation of the selecting signals filled with zeros. In that case the buffer register 22a will after reception of the next scanning signal from the scanning unit 11 in the exchange 1 transmit a series of the digital zeros to the scanning unit 11. The reception of a series of digital zeros in the scanning unit 11 forms an indication for the processor 15 that no new selec¬ ting signal was stored in the buffer register 22a, so that still the same program signal has to be transmitted to said subscriber output 6a. In that case no further action of the control unit 10 is neces¬ sary. In case a digital code non equal to zero is received, than said code is recognized by the processor 15 as a program selecting signal and in that case the processor 15 has to control the control unit 10 in correspondence therewith such that the switching means 3a are switching the progra n signal corresponding to said digital code to the subscriber output 6a. Because the scanning unit 11 transmits sequentially scanning signals via the cable network to each of the subscriber stations and because the buffer registers 22a in said subscriber station are only transmitting their contents to the exchange 1 after reception of a scanning signal, the cable network 7a... 7m as well as the buffer re¬ gisters 22a... 22m are continuously tested on correct functioning. If an interruption occurs in one of the cable connections 7a... 7m or if one of the buffer registers 22a... 22m shows a defect, then the exchange will not receive a response to the transmitted scanning signal. Because of this active role of the exchange 1 it is possible to realize also a more extended communication between the subscriber stations 2a... 2m and the exchange 1. If for instance 8 bit shift re¬ gisters are used into said buffer registers, then as a whole 256 dif- ferent codes can be transmitted. A number thereof can be used in the above mentioned way for selecting programs, but other codes, not used for selecting programs can be used for transmitting condition signals and/or data signals. Condition signals may for instance be derived from a fire alarm circuit, a burglar alarm circuit, an alarm circuit for aged people etc. Data signals can be derived for instance from a key board for selecting view data signals, or can be generated as in¬ quiry signals or data signals of other type. The exchange 1 has to contain means for distinguishing between the various signals dependent on the used coding. Furthermore each of the subscriber stations has to contain means for generating the va¬ rious codes whereby the exact embodiment of this means is of less im¬ portance within the scope of the invention. As example in the sub¬ scriber station 2m besides the selecting means 21m additional selec¬ ting means 24π are Illustrated as well as input terminals 25m, 26π connected to the buffer register 22m. The additional selecting means 24m (which are also present in the subscriber station 2a indicated by 24a) may for Instance be used in case the exchange has also view data information available. Said view data information for instance can be supplied in the exchange to a separate bus line and through the selecting means 24m said bus line can be selected. The additional selecting neans are thereafter necessary to choose the correct page out of this view data information. Said additional selecting means can be embodied for instance as a key board 24m. The signals generated by said key board are stored in the shift register 22m and are transmitted to the exchange after reception of a scanning signal. The processor 15 will recognize these selecting signals and evaluate these signals such that the correct page from the view data information will be trans¬ ferred to the subscriber 2m. It is furthermore possible to use the key board 21m or 24m in another way. It is for instance possible that during a television broadcast a number of subscriber stations are involved in an inquiry. By generating a predetermined code by means of the key board 24m, which code is recognized by the processor 15 and evaluated in a special way, it is for instance possible that each of said subscriber stations gives an answer to a question asked during a television broadcast. It is for instance possible that the processor 15 after reception of a signal of this type supplies a suitable signal via a separate output 16 to a separate processor 17, in which said signal is further processed. It will be clear that the selecting means 21m can be combined with the additional selecting means 24m into one single key board by means of which all the necessary code signals can be generated. It is furthermore possible to couple a fire alarm circuit for instance through the terminal 25m to the register 22m. If a fire alarm should be raised, then this fire alarm circuit has to generate a predetermined code, which code is stored in the register 22m. After transmission to the exchange 1 the processor 15 will recognize this fire alarm code and will supply for instance via the output 16 a signal to the further processor 17 which in his turn will signal the fire alarm section of the fire brigade or something similar. In a similar way a burglar alarm circuit, an alarm circuit for aged people etc can be connected to the terminals 25m or 26m or to further not illustrated terminals. The alarm codes generated by these circuits OMP can activate the processor 15 to supply a suitable signal via the ad¬ ditional output 16 to the further processor 17. Not only alarm circuits can be coupled to the switching circuit according to the invention, also the gas meter, water meter and elec- tricity meter can be coupled through a suitable coupling circuit to one of these additional terminals 25m, 26m, resulting into the pos¬ sibility to read periodically the indication of said meters. This can be carried out for instance as follows: Each of said meters comprises a generator circuit generating a coded signal corresponding to the meter reading, which coded signal is stored into the buffer register 22m. After transference to the exchange 1 this coded signal is decoded by the processor 15 and in response thereto the scanning sequence of the scanner 11 is inter¬ rupted and a further scanning signal is transmitted to the same sub- scriber station. In this subscriber station in the meantime the first part of the meter reading is_ stored into the register 22n. and this first part of the meter reading is in response to the next scanning pulse transferred to the processor 15. Thereafter a number of scanning pulses necessary for transferring the whole meter reading are generated and at the end thereof the scanner 11 is controlled by the processor 15 such that the normal sequential scanning is conti¬ nued. The received meter reading is for instance processed by the further processor 17. It will be clear that this is not the only solution to realize a meter reading of this type within the scope of the Invention. In a preferred embodiment of the invention the processor 15 com¬ prises a memory, which for instance can contain several data about each subscriber station. Stored therein are for instance data about the programs a subscriber station is allowed to receive or about the fact if In a subscriber station alarm circuits, meter reading circuits etc are connected, or about the fact if the subscriber is allowed to receive beside the normal program signals also view data signals etc. Also this memory can have additional capacity for tem¬ porarily storing for instance the received meter readings. The processor 15 Is preferably implemented by means of a micro¬ processor. In that case the control unit 10 and the scanning unit 11 can be embodied in the form of a suitable coupling circuit controlled by the microprocessor. ~~ It will be clear that the condition signals generated by the circuits connected to the terminals 25m and 26m and by the additional selecting means, should be distinguishable. For a detailed explanation of the invention in the description above reference is made to an exchange in which the available program signals are supplied through a number of signal inputs 4a, 4b... 4n to a number of bus lines 5a, 5b... 5n. Thereby in principle one program signal is available on one signal input respectively on one signal bus line. However, it is always possible to applicate the in¬ vention in an exchange in which all the available program signals are supplied in frequency multiplex on one input of the exchange. In this case the exchange comprises for each subscriber at least a mixing stage and a controlled oscillator, which oscillator supplies an output signal to the first input of the mixing stage. The frequency multiplex program signals are supplied to the second input of said mixing stage. Dependent on the selecting signals received from the subscriber station the oscillator related to the subscriber station concerned is adjusted to such a frequency, that in said mixing station the program signal corresponding to the received selecting signals is transferred to the output frequency band of the mixing stage. Hereafter this program signal is then, in the same way as it is above described, received by the subscriber concerned. All the control processes which are described above can also be realized with an exchange of this type. Furthermore it will be clear that the invention can also be used with exchanges which make use of separate lines combined into a bus for transferring the program signals as well as multiplexed program signals onto one or more of said lines. OMPI

Claims: C L A I M S . 1. Switching system, comprising an exchange and a number of sub¬ scriber stations, connected to said exchange through a cable network, whereby each subscriber station comprises selecting means for gener- ating selecting signals for selecting one out of a number of program or data signals available in the exchange, which selecting signals are stored into a buffer register, and the exchange comprises scanning means for scanning the buffer registers and control means for deriving control signals from the selecting signals read out of said buffer registers for controlling switching means in the exchange such that the program or data signals selected by means of the se¬ lecting signals are transferred from the exchange through the cable network to the subscriber concerned, characterized in that said buffer registers for the selecting signals are positioned into the subscriber stations, the scanning means are sequencially transferring scanning signals via the cable network to each of the subscriber stations, and the buffer registers are activated by said scanning signals to transmit the therein stored signals. 2. Switching system according to claim 1, characterized in that after or during the transmission of the buffer register contents to the exchange a special code is stored into said buffer register. 3. Switching circuit according to claim 1 or 2, characterized in that in stead of the selecting signals also condition signals or data signals which are not related to program selection can be stored into the buffer registers, which conditon or data signals can be transfer¬ red to the exchange in the same way as the selecting signals, whereby the exchange comprises means for distinguishing between said se¬ lecting signals and the condition or data signals which are not re¬ lated to program selection. 4. Switching system according to claim 3 characterized in that the exchange comprises means for interrupting the scanning sequence of the scanning means after reception of a predetermined condition signal or data signal from a subscriber station and for transferring further scanning signals to said subscriber station. OMPI

Inventors: DE ROO MINNO
Applicants: DELTAKABEL BV, ROO MINNO DE, DE ROO MINNO
Application year: 1982
Main classification: H04N7
IPC codes: H04N7, H04Q9