A METHOD AND APPARATUS FOR TRANSFERRING THE SAME INFORMATION TO A PLURALITY OF RECEIVERS

Abstract: A subscriber station (1) functioning as a concentrator is connected to subscribers (3) and is connected via trunk lines (4) to a centrally placed transit exchange (5) establishing connections, by reason of a given command, between a source (8) sending special information and a trunk line pointed out as being idle. The subscriber station includes a trunk line economizing apparatus (15-29) investigating each time a subscriber calls the source whether one of the trunk lines is already connected to the source. If no such connection is determined, the source and the calling subscriber are conventionally connected to a trunk line pointed out as being idle, the number of this line being intermediately stored in a memory unit (20) associated with the economizing apparatus. If it is determined at the investigation that the special information is already being transferred to the subscriber station, the subscriber calling the source is connected to the trunk line whose number is intermediately stored in the memory unit. The economizing apparatus includes a circuit (27) for cancelling the intermediate storage when the special information is no longer received by any of the subscribers. Independent of the number of subscribers receiving the special information, only a single trunk line is taken into use, and the central transit exchange is only loaded with a single connection establishment.

Description: A METHOD AND APPARATUS FOR TRANSFERRING THE SAME INFORMATION TO A PLU- RALITY OF RECEIVERS TECHNICAL FIELD The present invention relates to a method and apparatus for transferrin the same information to a plurality of receivers, telecommunication con nections being established due to given commands / for connecting a sour sending said information to a centrally placed transit exchange to re- ceiver-subscribers - which are each connected via a subscriber line to one of a number of peripherally placed subscriber stations, each sta tion being connected via its trunk lines, identi able b trunk line numbers, to said transit exchange. Examples of said information source are speech machines, which send in- formation such as news, weather conditions etc to a telecommunications network or give directions in conjunction with internal network intei— ferences. A nodal point at which information from several subscribers participating in a conference call is added for being transmitted to . the conferring subscribers and possibly to further subscribers who only listen, may also be regarded as an example of said information source. Connecting the information source to the respective subscribers is here by ordered conventionally, e g by the subscribers call signal or by means of a centrally based control unit for establishing connections for conference calls or interference information. BACKGROUND ART A telecommunications network is usually dimensioned so that said periph¬ erally placed subscriber stations function as concentrators with regard to traffic between the subscribers and the centrally placed transit ex¬ change. A smaller number of trunk lines are arranged than what would be needed if all the subscribers spoke simultaneously in pairs with each other via the centrally placed transit exchange. A certain risk is thus accepted for congestion of traffic in the establishment of- connections where trunk lines are included. The more trunk lines there are, the less risk of congestion and the more expensive the communications network. The "trunk line" concept is usually present in conjunction with commu¬ nications networks distributed in space, i e the exchange and transfer of the same trunk line mostly being used for both transfer directions. But as is known, there is also the four-wire sys- tern, in which a trunk line is only used for one transfer direction. In communications networks distributed in space .and time, e g integrated switching transmission CIST) systems for pulse code modulation (PCM), the trunk lines each correspond to a time slot in a time multiplex sys¬ tem selected for the network, whereby the information transmission is usually one-way and the exchange function executed in a digital mode- In network dimensioning calculations, an information source of the kind mentioned above has so far been treated as a plurality of separate sub¬ scribers with special problems. In political crises, for instance, the news speech machine is subjected to traffic peaks, and thereby it exists a great risk of communication congestion as -soon as the trunk lines are engaged. The connection of a speech machine to an analog telecommuni¬ cations system has been proposed, e g in an article "Anlaggning for telenytt" by B Bjurel, published in TELE, the Swedish Telecommunications Administration Technical Journal, 1958, pages 255-256, the treatment of the speech machine as a plurality of subscribers also includes the cen¬ trally placed transit exchange equipment. Connecting a speech machine to a digital time multiplex system has been proposed, e g in the Swedish Patent Application 7506811-4, the time stage of the system being dimen¬ sioned and controlled such that the speech machine phase should not need more time stage hardware than that required for a single subscriber. However, there is the great disadvantage in conventional analog and digital systems that each subscriber calling a speech machine is con¬ nected to it via a trunk line or time slot which is assigned solely to the associated call signal. The result of a political crisis can thus be that exactly the same news service is transferred on all trunk lines or time slots. DISCLOSURE OF INVENTION In the solution now proposed for achieving the object mentioned in the OMPI introduction, which is characterized by the features of the claims, onl a single trunk line is occupied independent of how many subscribers con nected to the same subscriber station receive the information generated by a speech machine. The function and treatment of the speech machine a a single special subscriber thereby extends right up to the peripherall placed subscriber station. The connection of the speech machine to the telecommunications network decreases rather than increases the risk of system, congestion. Further to this, the work load of the central transi exchange equipment also decreases, since it does not establish any con- nection to the speech machine if one of the trunk lines is already con¬ nected to it. BRIEF DESCRIPTION OF DRAWING The invention will now be described in detail while referring to the appended drawing. Apart from a portion of a conventional telecommunica¬ tions network, which includes subscribers, subscriber lines, a concen- trator, trunk lines and a speech machine, the drawing also shows a trunk line economizing apparatus connected to the concentrator. MODE FOR CARRYING OUT THE INVENTION The drawing illustrates a subscriber station 1 conventionally connected to subscribers 3 via subscriber lines 2 identifiable by means of sub¬ scriber numbers, and to a centrally placed transit exchange 5 via trunk lines 4 identifiable by means of trunk line numbers. The number of trunk Lines is less than the number of subscribers, and subscriber lines, i e the subscriber station is a concentrator. Telecommunication connections between the subscriber lines and trunk lines are established by means of a switch 6 in the subscriber station. The switch is operated conven- tionally by a marker 7 receiving the connection establishment informa¬ tion. The drawing solely shows the condition where one of the subscrib¬ ers 3 with the subscriber line number A is calling a subscriber with number B, who is not one of the subscribers 3, and who is reached by means of the central transit exchange 5. The drawing does not show the transit exchange in detail, and neither does it show that the exchange is connected to the remaining subscribers in the telecommunications network, either through further trunk line groups and subscriber statio or directly through further subscriber lines. As the sole one of all terminals which the subscribers 3 reach with the aid of the central ex¬ change,, there is shown on the drawing a speech machine 8 sending a spe- cial service, e g news. With the aid of conventional subscriber line circuits 9, through which the subscriber lines are connected to the subscriber line side of the switch, the calling subscriber's number A is registered in a first re¬ gister 10 and the called subscriber's.number B -is registered in a secon register 11. With the aid of conventional trunk line circuits 12 throug which the trunk lines are connected to the trunk line side of the switc it is registered in a first flip-flop 13, the bistable position of whic (denoted by "a" on the drawing) generates a logical "1" or "0" signal, whether there is an idle trunk line or not, respectively. The number of the trunk line which is to be used in the subsequent connection establi ment is registered in a third register 14. As normal connection establishment information, the marker 7 receives the number A written into the register 10 as well as the trunk line num ber written into the register 14. As will be seen from the drawings, th latter number is transferred, via a first AND gate 15 the function of which is described Later on. A normal connection establishment involves that the number B written into the register 11 is transferred to the central transit exchange 5 via a second AND gate 16, the function of which will be described later on, through the switch 6 and either throu the trunk Line pointed out by the register 14 or a signalling trunk lin intended solely for- signalling. A normal connection establishment furth involves the central transit exchange conventionally achieving that the subscriber identified with the number B is called and connected to the trunk line pointed.out, and that the subscriber line with the number A is connected in the switch 6 to the trunk line pointed out by the re¬ gister 14. Further to the mentioned substantially conventional communications net¬ work parts, the drawing also illustrates a third AND gate 17 forming a change-over switch together with said first AND gate 15, a special service command sender 18, a signal generator 19 and a memory unit 20, all of which are included in a trunk line economizing apparatus in ac¬ cordance with the invention. Said command sender 18 includes a fourth register 21 for constantly sto ing the special subscriber number B identifying said speech machine 8, and a first comparator 22 with its inputs connected to outputs on the registers 11 and 21 and its output constituting the output of the comman sender. When one of the subscribers 3 calls the speech machine 8, con¬ tents of the registers 11 and 21 are the same and the command sender out put is activated. Said signal generator 19 includes a second flip-flop 23, with its bi- stable position (denoted on the drawing by "a" and "b", respectively) connected to an input on a fourth and fifth AND gate 24 and 25, respect¬ ively. The second inputs of said gates -24 and 25 are connected to the command sender and their outputs constitute the outputs of the signal generator. The gate 24 is provided with an inverting output, which con¬ sequently generates a logical "1" signal if the command sender 18 is inactivated independent of the state of flip-flop 23 and if the flip- flop 23 is put in position "b" independent of the command sender state, and which inverting output generates a logical "0" signal only if the command sender 18 is-activated and the flip-flop 23 is in the position "a". The gate 25 generates a logical "1" signal only if the command sender 18 is activated and the flip-flop 23 is in the position "b", and generates a Logical "0" signal if the command. sender is inactivated in- dependent of the state of flip-flop 23 and if the flip-flop 23 is in position "a" independent of the command sender state. Said memory unit 20 includes a fifth register 26 and a second comparator 27 which compares the contents of the registers 14 and 26 and puts the flip-flop 23 in.the position "b" when the contents are equal. On the drawing, there is indicated by means of signal inputs 28 that the in¬ formation input of the register 26, which is connected to the output of the register 14, is activated for registering if the flip-flop 13 is set in the position "a" and the signal generator gate 25 generates a logical "1" signal. By means of a signal output 29 it is indicated that OMPI the register 26, due to a terminated registration, generates a signal which puts the flip-flop 23 in position "a". The information output of the register 26 is connected to the marker 7 via said gate 17, which is provided with an inverting control input. The three conventional registers 10, 11 and 14 connected to the subscrib er line circuits and trunk line circuits are of the destructive type, i e a shift of the registered contents to the marker and switch erases these contents, while the memory unit register 26 is of the non-destruct ive type, i e its contents can be shifted to the marker repeatedly until the contents is changed due to a new registration. The contents of the re gister 14 can be shifted in parallel to the marker 7 and register 26, b registration in the register 26 achieves no equality signal from the co parator 27, since the contents of the register 14 is erased when the re gistration in register 26 is terminated. For the sake of clarity, no su scriber station control unit is shown on the drawing, this unit activat ing said conventional registers 10, 11 and 14 for writing and reading. The subscriber station provided with the trunk line economizing apparat operates in the following manner: If the register 11 contains an arbitrary subscriber number B which iden tifies a subscriber not- shown on the drawing, the comparator 22 does no generate an equality signal, and the gate 24, independent of the state of the flip-flop 23, generates a logical "1" signal, and the gate 25 a logical "0" signal. Registration in register 26 and information transfe via gate 17 are blocked. The gates 15 and 16 are activated if an idle trunk line is available, i e if the flip-flop 13 is put into position "a" and the idle trunk Line's number is intermediately stored in the register 14. A normal connection establishment is executed. As will be described, the flip-flop 23 is set- in the positions "a" or "b" if one or none of the. trunk lines 4, respectively, is connected via the central transit exchange 5 to the speech machine 8. If.the flip-flop 23 is put in the position "b", if the register 11 inte mediately, stores the B number identifying the speech machine- 8 and if OMPI an idle trunk line is pointed out, then the comparator 22 generates an equality signal and the gates 24 and 25 generate -logical "1" signals. A normal connection .estabLishment between the calling A subscriber and th speech machine -is initiated. The register 26 is simultaneously activate for writing so that the contents of the register,-14 is transferred ther to. When the writing operation has been carried out, the flip-flop 23 is set to the position "a" as indication that the one of the trunk line 4 whose number is stored in. the register 26 is being-used to transfer t special service coming from the speech machine 8. If the flip-flop 23 is put to the position "a" and if the register 11 i termediatelyy stores the B number identifying the speech machine 8, the comparator 22 generates an equality signal and the gates 24 and 25 ge¬ nerate Logical "0" signals. The gates 15 and 16 block initiation of a normal connection establishment. On the other hand, gate 17 is activate for transferring the number which is intermediately stored in the re¬ gister 26 and identifies the trunk line already connected to the speech machine. Even if the trunk line circuits.12 point out an idle trunk lin at this instant, the associated number intermediately stored in the re¬ gister 14 reaches neither the marker 7 nor register 26. The comparator 27 does not determine any equality, since intermediate storing by the register 14 of-the number of an engaged trunk line is precluded. When none of the subscribers 3 is listening to the. special service any more, the trunk line circuits 12 sooner or later point out the trunk line as being idle, the number of which has up to now been intermediate ly stored in the memory unit 20. Then the comparator 27 generates an equality signal which puts the flip-flop 23 into position "b". By means of the proposed trunk line economizing apparatus it is possible to connect all subscribers 3 simultaneously to the speech machine 8 whil using a singLe one of. the trunk lines 4 and without loading the central transit exchange 5 more than once. OMPI

Claims: WHAT WE CLAIM IS: 1 A method of transferring the same information to a plurality of receivers, telecommunications connections being established due to given commands, for connecting a source sending said .information to a centrally placed transit exchange to receiver-subscribers which are each connected via a subscriber line to one o -a number of peripherally placed subscriber stations, each station being connected via its trunk lines,, identifiable -by trunk line numbers, to said transit exchange, characterized by: executing a search due to each command for ascertaining whether there is a trunk line engaged already for transferring said information to said subscriber station, .pointing out conventionally an idle trunk line connected to the sub¬ scriber station, if no already established connection has been determin¬ ed by said search, connecting said information source to the trunk line pointed out, immediately storing the number of the trunk Line pointed out, connecting the subscriber lines defined by the commands to the trunk line whose number is intermediately stored and cancelling said intermediate storage by reason of the information no longer being received by any of the subscribers. 2 Apparatus for transferring, in.accordance with claim 1, the same information to a plurality of receivers, telecommunications connections being established due to given commands, for connecting a source (8) sending said information to a centrally placed transit exchange (5) to receiver-subscribers. (3) which are each connected via a subscriber line (2) to. one of a. number of peripherally placed subscriber stations, each station being connected via trunk lines (4), identifiable by trunk line numbers, to said transit exchange, said subscriber station (1) in¬ cluding a switch/marker (6/7) for connecting an arbitrary associated subscriber line to an arbitrary associated trunk line, and including trunk line circuits (12) for pointing out idle trunk lines, characterize in that the apparatus comprises a) a signal generator (19) which, due to each command, sends a first or a second signal, respectively, indicating that there is or is not, a trunk line engaged already for transferring said information to said subscriber station, b) a memory unit (20) for, solely at the reception of said second signal, registering and intermediately storing a number identifying a trunk Line pointed out as idle with the aid of the trunk line circuits (12) and for achieving, due to a terminated registration, that said signal generator (19) sends the first signal, c) a change-over switch (15, 17) for transferring -to said switch/mark er (6/7}.,on reception of said first signal, the intermediately stored number in said memory unit (20) and, on reception of said second signal, said number identifying an idle trunk line, d) a gate means (16) for, solely on reception of said second signal, ordering the central transit exchange (5) to connect said information source (8) to said, trunk line pointed out as being idle, and e) a circuit (27) which effects that said signal generator (19) sends the second signal when the trunk line circuits (12) once again point out as being idle the trunk Line whose number is intermediately stored in the memory unit (20). OMPI

Inventors: FAERJH ARNE F
Applicants: ERICSSON TELEFON AB L M, FAERJH ARNE F
Application year: 1981
Main classification: H04M11
IPC codes: H04M3, H04Q3