Patent GB-100113-A (GB)
Title: Improvements in or relating to Semi-automatic Telephone Exchange Systems.
Inventor: HULTMAN CARL AXEL WILHELM
IPC: H04M3/62
Filed: 1916-02-22
Abstract: 100,113. Hultman, C. A. W. Feb. 23, 1915, [Convention date]. Semi-automatic exchange systems.-In systems of the kind in which connexions are established by means of numerical selectors under the control of register devices set from an operator's keyboard, the trunks allotted to an operator's position are divided into a number of sub-groups, each having one register device associated with it. No switches are therefore required to select an idle register, the whole of the trunks in a sub-group being marked busy while the register is in use. The sub-groups may be arranged in main groups, all the trunks in the main groups being marked busy when a call is made in any of its sub-groups, the sub-group including the calling trunk being marked busy until the connexion has been completed, while the other sub-group or sub-groups in the same main group are made available as soon as the call has been attended to by the operator. Calls may be received simultaneously in two or more main groups but only one of the calls at a time can be switched through to the operator's speaking set. In the system described, the trunks are divided into two main groups PS1, PS2, Fig. 1, each containing two sub-groups G1, G2; G3, G4, the trunk being a member of the sub-group G4. The operator's keyboard set S can be associated by means of relays, such as RR1, RR2, Fig. 2, with any of the four register devices, such as RE, Fig. 2, individual to the four sub-groups of trunks respectively. The register shown is that associated with the sub-group G4. The invention is shown applied to a system of the kind described in Specification 4285/15, in which the wipers of the connector are normally positioned centrally with respect to the terminals of four groups of subscribers, and can be moved right or left and up or down to select a subscriber in any of the four groups. The system described uses largecapacity connectors, each serving 10,000 subscribers, group selectors being also employed so that a total capacity of 100,000 lines is provided for. Connexion of trunk to operator's speaking set and register device. When a calling preselector finds an idle selector trunk having access to an idle register current flows over the test-lead c, point z<1>, call relay LaR1, relay M1R1, contact 301 of a relay MR2, and contact 302, controlled by the plug switch of the operator's speaking set, to earth. The opening of contact 302 marks the whole position engaged when the operator leaves her place. The test-relay of the calling pre-selector short-circuits part of its resistance, and as the resistance of the relay LaR1 is small compared with that of the relay M1R1, the potential of the bus-bar m<1> is such as to mark busy all the trunks in the right-hand sub-group G4. The relay M1R1 closes contact 303 so as to mark busy all the trunks in the sub-group G3 also, and the call-relay LaR1 lights the lamp La1 over bus-bar ls1 and contact 307. If the operator is free, or as soon as she is disengaged from a call in the main group PS1 the relay M1R1 also energizes the operator's speaking relay ER1, which (1) connects the operator's set to the bus-bars t<1>, t<2> common to the main group PS2, (2) opens the circuit of the corresponding relay ER2 associated with the group PS1 so that no call from this group can be connected to her set, and (3) connects the interrupter I4 to the bar ls1 so that the lamp La1 flashes. The relay LaR1 also connects the catling-trunk to the bars t<1>, t<2> so that the operator can enquire the connexion wanted. If a call bad been received from the sub-group G3, the relay M1R1 would have been energized over its lower winding and a contact of a relay MR3. Similarly, a call from either of the sub-groups G1, G2 would have energized one or other of the windings of the relay M2R1, associated with the operator's relay ER2. The relays MR2, MR3, &c., associated with their respective registers, prevent a call from being received in a sub-group until the corresponding register is free to set up a further connexion. Setting of register by operator. The operator sets up the wanted number on her keyboard, thereby grounding one or more wires of each set leading to the contacts of a rotary switch M, which controls the setting of the registers. The particular register RE to be set has been determined by the relay LaR1 closing at contact 314 a circuit for the register relay RR1 associated with the calling- group. The operator then depresses the starting- key SK1 individual to the trunk a, b, thereby (1) closing a locking-circuit for the register relay RR1, which connects the wires from the switch M to the magneto of the register RE, (2) closing the circuit of the motor M' driving the switch M, whereby the registers RE1 - - RE5 are simultaneously moved a number of steps corresponding to the depressed keys, (3) energizing a relay UR1, which locks up over the test lead c and cuts off the call relay LaR1 and all connexion of the calling-line to the operator's set. When the register RE5 leaves its normal position, the relay MR2 is energized, causing the lamp La2 to glow and marking the corresponding sub-group of trunks G4 non- selectable. Control of selector by register. The depression of the starting-key SK1 also energizes the relays R1, R2, which (1) lock up until the connexion has been established, (2) disconnect the calling-line from the selector, (3) connect the a and b leads of the selector over the bus-bar S2, S3 to the relays LR3, LR4, which effect the return movement of the registers RE2 &c., (4) connect the d-lead to the spring of relay V, and (5) close the circuit of the clutch magnet MK3 of the group selector over contact 329, bar s5, contact 25 of register RE1, and part IV of the auxiliary switch O in its second position. As the selector rotates, the register magnet RE1 receives impulses over part I of switch O, and as soon as this register reaches its normal position, the opening of contact 25 disconnects the clutch magnet MK3, and the closing of contact 26 energizes the relay R3, which supplies current to the clutch magnet MK4 of the hunting-switch of the selector, of which one level has been brought into circuit by the numerical switch. The lines to which this level gives access are tested successively by a relay LyR3. When an idle line is reached, the test relay is energized over a resistance R4 and short-circuits the greater part of its winding so as to mark the appropriated line non-selectable to other selectors. At the same time, it de-energizes the relav R3 so as to open-circuit the clutch magnet MK4 and stop the selector. The relay R3 also controls the magnet OE, so that the de-energization causes the auxiliary switch to move to its third position, in which a relay O2E2 is energized. Connector. One or other of the clutch magnets M1K1, M1K2, Fig. 3, which move the connector to right and left respectively, is now energized according to the setting of the thousands register RE2. If this register has been set from six to ten steps from its normal position, so that the contact 32 controlled by the cam g' is open, current is transmitted through contacts 158, 159 to the outgoing d-line and energizes a relay S1R1 which controls the clutch magnet M1K1; but if the register RE2 has been set from one to five steps from its normal position, a relay V is energized over the contact 32 and diverts the starting-current through a contact 174 to the outgoing b-line, so that the relay S1R2, controlling the magnet M1K2, is energized. A relay HR1 is energized in series with the magnet M1K1 or M1K2, and, as soon as ti-e connector leaves its normal position, a contact 168 energizes a relay R, which locks itself up and energizes a self-locking relay BR1. As the connector moves to right or left, two pairs of springs S1 send back impulses which move the registers RE2, RE3 forward until they regain their normal position. At first, only the impulses from the lower pair of springs (transmitted as the connector passes from one thousand division to the next) are operative, these impulses returning over the a-line to the relay LR3, which repeats them to the register RE2. The impulses from the upper pair of springs (transmitted as the connector passes from one hundreds group to the next) pass back, either through the contact 165 and the b-line, or through the contact 177 and the d-line, according to the direction in which the connector is moved, to the relay LR4, which controls the register RE3; but at first this circuit is inoperative, being open at the contact 44, and it is only when the register RE2 regains its normal position and closes the contact 44 that the restoration of the register RE3 begins. Since the connector only passes over five " thousands " divisions in whichever direction it is moved, it follows that, when the register RE2 has been set less than six steps from normal, it must be given five preliminary steps before the connector reaches the operative part of its travel. This is provided for by five preliminary contacts (not shown) which are swept by the lower pair of springs S1 at the beginning of the leftward movement of the connector. When the restoration of the register RE3 is complete, the contact 33 opens the circuit of the relays 02E2, V, and S1R1 or S1R2, bringing the connector to a stop, and the de-energization of the relay HR1 open-circuits the magnet MB1, which applies a brake or holding- clutch to the horizontal motion mechanism. At the same time, the magnet OE, which is controlled by the relay 02E2, de-energizes and moves the auxiliary switch to its fourth position. The vertical setting of the connector is now controlled in the same way by the tens and units registers RE4, RE5, the upward movement magnet M2K1 or the downward movement magnet M2K2 being set in action by the relay S2R1 or S2R2, and restoring impulses being sent back by the springs S2, and when the register RE5 regains its normal position, the conne