Patent GB-877246-A (GB)
Title: Improvements in or relating to telephone traffic concentrators
IPC: H04Q3/52
Filed: 1959-07-24
Abstract: 877,246. Automatic exchange systems. LIBOIS, L. J., and LUCAS, P. M. July 24, 1959 [July 26, 1958], No. 25543/59. Class 40 (4). In an automatic satellite (non-exchange) having subscribers' gates, responsive to the service condition of the subscribers' lines, and trunk circuits, responsive to the connection condition of the trunks to the parent exchange, which are connected to the rows and columns respectively of a gas-tube cross-point matrix, means are provided for connecting at random to an idle trunk a calling subscriber's line or an idle called line the number of which is sent from the exchange, and for disconnecting a trunk the number of which is sent from the exchange, the number of a calling line and that of a connected trunk being sent in a serial code to the exchange, whereas that of a called line to be connected and of a trunk to be disconnected are received in a serial code from the exchange. General outline of operation, Fig. 1.-The subscribers' register 7 operates as a binary counter driven by the pulse generator 16 and delivers pulses cyclically to the outlets 81 to 144 of the distributer 8 to scan the gates 2 of the subscribers' lines. A scanning pulse passes via the gate 2 of a line in calling condition to fire one of the tubes 13 of the matrix 10, thus extending the calling line to a free trunk circuit 23, the identity of which is entered in the trunk register 17 via the trunk coder 15. This scanning pulse also stops the register 7, thus leaving the identity of the calling line stored therein. The test register 4 is then driven by the pulse source 5 to interrogate, via the test decoder 6, the subscriber register 7 and the trunk register 17 and to transmit the identity of the calling line and that of the seized trunk to the exchange over lead 20 in binary code. When a call is to be extended to one of the subscribers of the satellite, the number of the line concerned is received over lead 22 in binary code. The corded number is preceded by a start pulse, receipt of which stops the driving of register 7 by the pulse source 16 and prevents the marking of the outputs of the distributer 8. The test register 4 is driven by the pulses of the received number code to pulse the outputs a 1  to a b  of the decoder 6 in succession and the wanted number is entered into the subscriber's register by the pulses repeated over lead 31 at the same time, whereafter the pulse on a 7  removes the inhibition from the outlets of distributer 8 and effects the firing of a tube 13 to connect the wanted line to a free trunk. The identity of the seized trunk is signalled to the exchange as in the case of a calling line connection. The code number of a trunk to be disconnected has a start pulse of opposite sign to that of the wanted line signal, and this results in the test register 4 being set immediately to mark outlet a 8  of the test decoder 6. The pulses incoming to the register 4 cause it to pulse outlets a 9  to a 12  in succession and the trunk number is entered in trunk register 17, whereafter the pulse on a 13  is ineffective. The pulse produced on terminal 183 by the trunk decoder 18 causes the required disconnection to be made. Detailed operation: subscriber initiates call.- Provided the trigger circuits 32 and 33 are both in the rest condition, the output of the multivibrator 16 (Fig. 4) drives the six trigger circuits 71 to 76 of the subscriber's register 7 as a binary ring counter. This results in the terminals 81 to 144 of the distributer 8 being pulsed cyclically, the respective pulses being extended to the subscriber's gates such as 2 (Fig. 2) over leads such as 182<SP>1</SP> to scan those gates. When a line is not connected to a trunk there is no current flow in the centre winding of transformer 201 of its gate 2, and the scanning pulse passes through the " and " gate 204. Closure of the loop of such a line operates its detector 203 and the scanning pulse passes via " and " gate 205, " or " gate 207 and amplifier 209 to fire a tube 13, thus extending the calling line to a free trunk circuit over a lead 12. Firing of the tube 13 inhibits the " and " gate 204 and increases the potential at the point 234 of the seized trunk circuit 23 (Fig. 6). This increase is differentiated by capacitor 235 and resistor 236, the resulting positive pulse applied over lead 253 to the trunk coder 15 (Fig. 5) setting the four trigger circuits 171 to 174 of the trunk register 17 in accordance with the identity of the seized trunk. The scanning pulse passed by the " or " gate 207 (Fig. 2) also sets the trigger circuit 32, thus reducing the potential of lead 67 (Fig. 4) so that the pulses from the multivibrator 16 cannot step the register trigger circuits 71 to 76 away from the settings indicative of the calling line. Setting of the trigger circuit 32 also removes the inhibiting potential applied to the multivibrator 5 (Fig. 3) via the " and " gate 65, and this multivibrator then drives the trigger circuits 41 to 44 of the test register 4 so that pulses appear successively at the outputs a 0  to a 15  of the test decoder 6 to test the condition of the subscribers' register 7 and the trunk register 17. For example, if the trigger circuit 71 is in the rest condition the pulse appearing at a 1  passes through the " and " gate 49 and diode 52 to the lead 51, whereas if it is in the set condition, the pulse passes through " and " gate 49<SP>1</SP> and diode 52<SP>1</SP> to the lead 51+. Thus, in respect of the pulses on a 1  the a 6 , pulses appear on 51- or 51+ according as the trigger circuits 71 to 76 respectively are at rest or set. The pulses on a 9  to a 12  test the trunk register 17 in like manner. The leads 51- and 51<SP>+</SP> terminate in the signal sender 29 (Fig. 7) at the bases of transistors 292 and 291, respectively. A positive pulse 51- renders the transistor 292 conductive whereupon transistors 294 and 296 also conduct, point 298 goes positive and 297 negative and a negative current in the direction of the arrow 202 flows in the signalling line 20. Similarly, a positive pulse on 51+ results in a positive current (arrow 201) in the line 20. The signal receiver 928 (Fig. 7) at the exchange in response to the negative current produces a positive pulse at point 284, and in response to the positive current a positive pulse at point 283. The pulse appearing at outlet a 15  of the test decoder 6 (Fig. 3) passes via leads 47, 48 to restore the trigger circuits 171 to 174 (Fig. 5) and the trigger circuit 32 (Figs. 2, 3). With the trigger circuit 33 (Fig. 3) also in its rest condition, the " and " gate 65 passes the inhibiting potential to the multivibrator 5. With trigger circuit 32 restored the multivibrator 16 again drives the subscribers' register 7 to resume scanning. Establishing connection to a wanted subscriber.-The number of the wanted subscriber is sent by the exchange sender 929 (Fig. 8) as a series of six current elements (positive or negative) on line 22, preceded by a positive start pulse. The positive current elements are repeated by the receiver 28 as positive pulses on lead 31+ and the negative ones as positive pulses on lead 31-. These pulses pass via " or " gate 37 (Fig. 3) and pulse repeater 38 and thence via " and " gate 39 and lead 40 to set trigger circuit 33. As the start pulse is positive the " and " gate 66 remains closed. With trigger circuit 33 set the potential of lead 67 is reduced, thus preventing the multivibrator 16 from driving the subscribers' register 7 (Fig. 4). In addition the reduction of potential on lead 34 renders the diodes 711, 712 . . . conductive, thus inhibiting the outputs of the subscriber's distributer 8. Restoration of the pulse repeater 38 after each received pulse advances the test register one step and pulses appear successively at outlets a 0  to a 6  of the test decoder 6, the multivibrator 5 remaining inhibited (32 in rest condition). Each of the trigger circuits 71 to 76 is set to the condition corresponding to the sign of the relevant received pulse. Thus, if circuit 71 is in the rest condition and the first identification pulse is positive, the " and " gate 49 receives positive potential from outlet a 1  and from lead 50, and passes a positive pulse to the " and " gate 9, which also receives a positive pulse on lead 31+. The output of the latter gate sets trigger circuit 71 to its operated state. If, however, circuit 71 is in its operated state, there will be no positive potential on lead 50, so that no output is obtained from gate 49 and circuit 71 remains in its operated state. The subscriber's register 7 is thus set in accordance with the wanted number. At the end of the sixth received identification pulse, a positive pulse appears at a 7  and is applied to the " and " gate 57, thus restoring the trigger circuit 33 which removes the inhibition of the outputs 81 to 144 of the subscriber's distributer 8 (Fig. 4), and to the gates 2 (Fig. 2) of all subscribers over lead 35. If the wanted subscriber is free, the marking from the distributer 8 on lead 182<SP>1</SP> passes via " and " gate 204, and the pulse from a 7  passes via " and " gate 206, " or " gate 207 and amplifier 209 to effect connection to a free trunk as in the case of a calling subscriber. This pulse also sets the trigger circuit 32, whereupon the multivibrator 5 drives the test register and the identity of the seized trunk is sent to the exchange as in the case of a calling line. Disconnection of a trunk line.-The identity of the trunk is sent from the exchange in the form of four positive and negative pulses preceded by a negative start pulse. The negative start pulse sets trigger circuit 33 and also passes via " and " gate 66 to set the trigger circuit 44 of the test register 4, thus causing a pulse to appear on outlet a 8 . The received pulses over line 22 cause the test register 4 to set the trunk register 17 to the trunk concerned in the same manner as the subscribers' register is