FR2529045A1 - Transmission system linking PBX with external circuits - includes input and output buses for each unit linked via controlled switching unit - Google Patents

Abstract

The transmission system ensures a bidirectional connection between two or more terminal units of different hierarchial level (1,2) and between additional circuits such as the transmitters and receivers of multifrequency and tone signals. The terminal units are grouped into two sections (1,2) within which the terminal units have the same hierarchy level. The data receiving inputs of all the terminal blocks are connected in each section to a first bus (4,5). A switching circuit (23) allows either the connection of the first and second bus of one assembly to the second and first bus of the other assembly respectively, or the isolation of one pair of buses from the other pair.

Description

TRANSMISSION DEVICE BETWEEN TERMINATIONS
HIERARCHISES OF A TEMPORAL COMMUNICATION SYSTEM
The present invention relates to a digital transmission device between hierarchical terminations of a time communication system.

 Generally, a MIC time switch consists of a set of terminations, such as subscriber line equipment, trunks, and ancillary circuits such as transmitters and receivers of multifrequency signals or tone signals, etc. ., these terminations being connected to two bus for receiving and transmitting signals, respectively. It is then necessary to use a connection network to route the data from the sending bus to the receiving bus at precise times, and thus allow bidirectional conversation between two terminations. This connection network is generally made up of many fast circuits such as memories, addressing system, counter, etc. The price of this network is therefore relatively high and its use in a small capacity communication system is therefore very expensive vis-à-vis the cost price reduced to a price per termination.

 On the other hand, in most connection network transmission systems comprising terminations with different types and intensities of traffic such as networks and stations (hierarchical terminations), a time interval is systematically assigned to each network (high hierarchy) so as to be sure that you can handle a call if necessary. This constitutes a handicap for the traffic of posts with a weak hierarchy.

 The present invention relates to a device for transmission between hierarchical terminations of a time-based communication system of small capacity, which does not require a connection network, and of the lowest possible cost price.

 The present invention also relates to a transmission device of the aforementioned type making it possible not to significantly disadvantage the terminations with a weak hierarchy compared to the terminations with high hierarchy.

 The transmission device according to the invention, intended to ensure the bidirectional connection between two or more terminations of different hierarchies, or between terminations and ancillary circuits, these terminations being grouped according to their nature into two sets of terminations in each of which the terminations have the same level of hierarchy, the data reception inputs of all the terminations being connected in each of the two sets to a first bus, and the data transmission outputs of all the terminations being connected in each of the two sets to a second bus, this device comprising a switching circuit making it possible either to connect the first bus and the second bus of a set to the second bus and to the first bus, respectively, of the other set, or to isolate the buses of one set with respect to the buses of another set, while connecting together the two buses of each set.

 The present invention will be better understood on reading the detailed description of an embodiment taken as a nonlimiting example and illustrated by the appended drawing, the single figure of which is a simplified block diagram of this embodiment.

 The time communication system represented in the single figure of the drawing is for example a private telephone exchange and includes terminations which can be classified into two kinds: terminations connected to subscriber stations and terminations connected to networks ( public telephone network, specialized data transmission networks, etc. These two types of termination have different hierarchy levels, because networks require continuous monitoring because they have very high traffic and must be able to send their calls as soon as they show up, when stations usually have less traffic and can wait before getting their calls, and networks rarely communicate with each other, while stations communicate about as much with each other as 'with networks.

The communication system network terminations have been grouped into a set 1, and the station terminations have been grouped into a set 2. In set 1 only three terminations TRI, TR2 and
TR3 were represented. Overall 2, only three endings
TP1, TP2 and TP3 were represented.

 All terminations have data transmission outputs referenced E, and data reception inputs R.

 The inputs R of the terminations of assembly 1 are connected to a bus 3, and their outputs E are connected to a bus 4. The outputs E of the terminations of assembly 2 are connected to a bus 5, and their inputs E are connected to a bus 6.

 The transmission selection and reception selection inputs SE of each of the terminations of the set 1 are connected to a selection circuit 7, while the inputs SE and SR of each of the terminations of the set 2 are connected to a selection circuit 8. To simplify the drawing, a single circuit 7 and a single circuit 8 have been shown.

 An example of realization of circuits 7 and 8 is given below.

 The circuit 7 comprises three control terminals 9, 10, and 11 to which control signals are applied under the conditions explained below, these signals being produced by the control unit (not shown) of the communication system. Terminal 9 is directly connected to the SR input, as well as to the input of a three-state door 12, the output of which is connected to the SE input. Terminal 10 is connected to the input of another three-state door 13, the output of which is also connected to the input SE of the corresponding termination. Terminal 11 is connected to the input of a logic inverter 14, the output of which is connected on the one hand to the inverted input for bringing the high-impedance state of the gate 12, and on the other hand to the input of another logic inverter 15. The output of the inverter 15 is connected to the inverted input for setting the high impedance state of the gate 13. Thus the selection signal present on terminal 9 is always found connected to the SR input while the SE input is either connected to terminal 9 or to terminal 10 depending on the state of terminal 11.

 The circuit 8 comprises three control terminals 16, 17 and 18 to which are applied control signals produced by said control unit under the conditions explained below. Terminal 16 is connected to the input of a logic inverter 19, the output of which is connected on the one hand to the input of another logic inverter 20 and on the other hand to the reverse input for setting high-impedance state of a three-state gate 21. Terminal 17 is connected to the input of a three-state gate 22, the output of which is connected to the input SR of the corresponding termination, and whose inverted input for setting in the high impedance state is connected to the output of the inverter 20. Terminal 18 is connected, on the one hand directly to the input SE of the termination in question, and on the other hand to the input of the gate 21 whose output is connected to the aforementioned SR input.

 For a better understanding of the system, terminals 1 1 and 16 are separated; in fact the terminals il and 16 are connected together and therefore become a single terminal for the entire installation. Circuits 14 and 19 are the same as circuits 15 and 20.

 Buses 3 and 4 are connected to buses 5 and 6 via a switching circuit 23. This circuit 23 makes it possible to connect buses 4 and 5 to buses 6 and 3 respectively, or to isolate them therefrom, and in the latter case of interconnecting buses 4 and 3 on the one hand, and buses 5 and 6 on the other.

Circuit 23 has four doors with three states referenced 24 to 27 whose inputs and outputs are respectively connected to buses 5 and 3, 4 and 6, 4 and 3, 5 and 6. The inputs for setting the high impedance state of these four doors are connected, not shown, to the processing unit of the communication system (not shown either) which controls them as explained below.

 The communication system shown in the drawing also includes a circuit 28 for transmitting tones and messages connected to bus 3, a circuit 29 for detecting tones connected to bus 4, a circuit 30 for transmitting multifrequency signals connected to bus 3, a circuit 31 for receiving multi-frequency signals connected to the bus 5, and a circuit 32 for transmitting tones and messages connected to the bus 6. The circuits 28 to 32 are known per se and operate in the usual manner in the present communication system ; these circuits will therefore not be described in more detail.

 We will now study in detail the different modes of operation of the transmission device of the invention described above.

 10) Local operation. Any two subscribers each connected to a termination of set 2 converses with each other. Let TPI and TP2 be these two endings. The circuit 23 isolates the buses 5, 6 from the buses 3, 4 and connects the bus 5 to the bus 6, and advantageously connects the bus 4 to the bus 3 (this connection is not necessary for local operation, but allows independent operation inter - networks described below). To this end, the control unit forces the doors 24 and 25 to the high impedance state (open) and the door 27 (and if necessary the door 26) to the on state. Thus, buses 5 and 6 are interconnected, but are isolated from buses 3 and 4.

 The transmission of data from TP1 to TP2 uses a first time interval from buses 5 and 6, and the transmission of data from TP2 to TPI uses a second time interval from buses 5 and 6. A logic level "0" is applied to terminal 16 of each of the circuits 8 concerned. Thus, in each of these circuits 8, the door 21 is open and the door 22 is open. Consequently, each of the terminations TP1 and TP2 receives on its input SR a reception selection signal applied to the corresponding terminal 17, and on its input SE a transmission selection signal applied to the corresponding terminal 18. Several pairs of subscribers can therefore converse with each other, independently of the operation of the networks, within the limit of the number of time intervals of buses 5 and 6, two time intervals being taken by each pair of subscribers.

The circuit of the invention also allows, in local operation, teleconferencing between three or more subscribers. Let N be the number of these subscribers. Thanks to the device of the invention, just N time intervals of the buses 5, 6 are sufficient to ensure the teleconference link between these N subscribers. Indeed, if for example N = 3 and if we respectively call
Al, A2 and A3 these three subscribers, the first time interval is used by Al to transmit to A2 and A3, the second time interval is used by A2 to transmit to Al and A3, and the third time interval is used by A3 to send to Al and A2. Consequently, each of the subscribers can establish a conversation (two-way link) with the two other subscribers. We can easily verify that this possibility can be generalized to any number N of subscribers (of course within the capacity limit of buses 5, 6 ).

 20) Network operation. Any subscriber connected to a termination of set 2 establishes two-way communication with one of the networks connected to a termination of set 1. For example, the subscriber connected to termination TP1 communicates with the network connected to the termination TR3. In circuit 23, doors 26 and 27 are forced to the high impedance state, and doors 24 and 25 are turned on.

Thus, bus 5 is connected to bus 3, and bus 4 is connected to bus 6. A level "1" is applied to terminals 11 and 16 as well as the transmission selection and reception selection signals on the terminals 10, 13 and 9, 17 respectively. Thus, in circuit 7 of TR3 the door 12 is on and the door 13 in the high impedance state. In circuit E of TP1, the gate 21 is on and the gate 22 in the high impedance state. The reception selection signal is therefore applied to the inputs SE and SR of TR3, and the transmission selection signal is therefore applied to the SE inputs and
SR of TP1. All that is needed is a single time interval on all of the buses 3 to 6 to establish a bidirectional link between the subscriber connected to TP1 and the network connected to TR3.

 It is possible to establish a teleconference link between one or more TP1 station terminations and one or more TR1 network terminations. N time slots are used to establish the teleconference link between n terminations. If, for example, we want to establish the connection between TP1, TP2 and TRI, we use three time intervals. On the first time interval, TP1 transmits to TP2 (27 being closed) and TR 1 (24 being closed). On the second time interval, TP2 transmits to TPI (27 being closed) and to TRi (24 being closed). On the third time interval, TRI transmits to TP1 and TP2 (25 being closed).

 3) Local operation + network in the guard position Any two subscribers interact with each other, and on the other hand the tone transmitter circuit 28 is in communication with one of the networks. The circuit 23 is then in the same state as for the first operating case described above, that is to say that the buses 5, 6 are isolated from the buses 3, 4, and that the bus 5 is connected to the bus 6. A "0" is applied to terminal 16, and local operation is unchanged.

 The door 26 being made passable, the bus 4 is connected to the bus 3.

A "0" is applied to terminal 11, a reception selection signal is applied to terminal 9 and is found at the input SR of the chosen network termination. The tone transmitter circuit 28 can then send its signals to the input R of said network termination, using a time interval of the buses 3, 4. Teleconferencing is possible, as explained above.

40) Local operation + station in guard position. Two subscribers interact with each other, for example those connected to TP1 and
TP2, and another subscriber, for example the one connected to the TP3 termination, receives a tone signal. The circuit 23 is in the same state as for the third case above. The first two subscribers mentioned dialogue with each other using two time intervals of the buses 5, 6. The termination TP3 receives on terminal 16 of its circuit 8 a signal "0". Consequently TP3 receives on its input SR the reception selection signal applied to the terminal 17 of its circuit 8. The tone signals emitted by the circuit 32 arrive at the input R of TP3 using a time interval. Teleconferencing is possible, as explained above.

5) Network operation + station in the guard position. A subscriber, for example the one connected to the TP1 routing, is in two-way communication with a network, for example the one connected to the termination
TR2. In addition, another subscriber, for example the one connected to the termination
TP2, receives tone signals.

The circuit 23 is in the same state as for the second operating case above, that is to say that the bus 5 is connected to the bus 3, and the bus 6 to the bus 4. The subscriber of TP1 is in bidirectional communication with the TR2 network as in the second operating case, using a single time interval. In addition, TP2 receives on its entry
R the tone signals emitted by circuit 32, using a single other time interval, and a "0" is applied to terminal 16 of circuit 8 of
TP2, which causes the SR input of TP2 to receive reception selection signals.

60) Inter-network operation. Any two networks establish two-way communication, for example networks connected to the TRI and TR3 terminations. The circuit 23 is brought in the same state as for the third operating case above, that is to say that the buses 5, 6 are isolated from the buses 3, 4 and that the bus 4 is connected to the bus 3 A "0" is applied on terminal 11, and the inputs SE and SR of TRI and
TR3 respectively receive the transmission selection and reception selection signals. The output E of TRI sends the network data corresponding to the input R of TR3 over a first time interval, and the output E of TR3 sends the network data corresponding to input R of TRi over a second time interval. Teleconference link between several networks is done in a similar way to that described above for the first case of operation, using each time only one time interval.

 7) Dialing standby operation. One of the telephone sets warns, via its termination, the multifrequency signal receiver 31 over a time interval of the bus 5, and the tone transmitter 32 transmits to this station over the same time interval of the bus 6: this time interval allowing the analysis of the dialing coming from the termination in question and the simultaneous broadcasting of a tone (or a message) at this same termination.

The state of circuit 23 does not connect buses 5 and 6: circuit 27 is open.

 Thus, the transmission device of the present invention makes it possible, without a connection network, to establish bidirectional communication between a station and a network, over a single time interval, and in other cases of operation, to establish communications bidirectional between terminations of the same hierarchy, independently of the communications between terminations of another hierarchy, this using two time intervals each time. The device of the invention makes it possible to have in a MIC communication system operating with frames of thirty-two time intervals up to approximately twenty networks and one hundred and four stations with an average traffic of 0.172 Erlang per station. If frames of sixty-four time slots were adopted, the system capacity would be approximately forty networks and two hundred and fifty six stations with an average traffic of 0.173 Erlang per station.

Claims (7)

 1. Transmission device between hierarchical terminations of a time communication system, intended to ensure the bidirectional connection between two or more terminations of different hierarchies (1, 2), or between terminations and ancillary circuits (28 to 32) such as transmitters and receivers of multifrequency signals or tone signals, these terminations being grouped according to their nature into two sets of terminations (1, 2) in each of which the terminations have the same level of hierarchy, characterized in that the data reception inputs (R) of all the terminations are connected in each of the two sets to a first bus (3, 6), that the data transmission outputs (E) of all the terminations are connected in each of the two assemblies to a second bus (4, 5), this device comprising a switching circuit (23) allowing either to connect the first bus and the second bus of an assembly to the second bus and to the first bus, respectively, of the other set, or to isolate the buses of a set with respect to the buses of the other set, while connecting together the two buses of each set.  2. Transmission device according to claim 1, characterized in that the bidirectional link between a termination of one of the sets and a termination of the other set uses a single time interval.  3. Transmission device according to any one of claims 1 and 2, characterized in that the bidirectional link between two terminations of the same set uses two separate time intervals.  4. Transmission device according to any one of claims 1, 2 and 3, characterized in that the operation awaiting dialing from a termination requires only one time interval for the analysis of the dialing from the termination and simultaneous broadcast of a tone (or message) at the same termination.  5. Transmission device according to any one of claims 1 or 2, for teleconferencing between N subscribers connected to N terminations of the same set, characterized in that the teleconference link is provided by N time intervals.  6. Transmission device according to any one of the preceding claims, characterized in that said switching circuit comprises four doors (24 to 27) with three states disposed respectively between the second bus of an assembly (4, 5) and , on the one hand, the first bus of the same set (3, 6), and on the other hand the first bus of: 'other set (6, 3).  7. Transmission device according to any one of the preceding claims, in which the transmission selection (SE) and reception (SR) inputs of each termination are connected to a selection circuit (7, 8), characterized by the fact that this selection circuit comprises a first terminal (9, 18) receiving a reception selection signal for high hierarchy terminations (1), and a transmission selection signal for weak hierarchy terminations (2) , a second terminal (10, 17) receiving a transmission selection signal for high hierarchy terminations and a reception selection signal for low hierarchy terminations, and a third terminal (II, 16) receiving a "1 "for communications between terminations of different hierarchies and a" 0 "in other operating cases, the first terminal being connected on the one hand directly to the corresponding designation selection input (SR or SE) of the termination in quest ion, and secondly by a first three-state gate (12, 21) to the other selection input (SE, or SR) of the termination, the second terminal being connected to said other selection input by a second gate three states (13, 22), the third terminal being connected by a first logic inverter (14, 19) to the inverted input for bringing the high impedance state of the first three state gate, this first inverter being followed by a second logic inverter (15, 20) whose output is connected to the inverted input for setting the high impedance state of the second three-state gate.