Patent GB-191328362-A (GB)
Title: Switching Systems and Apparatus for Interconnecting Telephone Lines.
Inventor: ALDENDORFF FRITZ
Filed: 1913-12-09
Granted: 1915-07-15
Abstract: 28,362. Aldendorff, F. Dec. 9. Automatic exchange systems.-In order to reduce the time taken in finding a calling line, the wipers of a call-finder are arranged to rest normally at the middle point of the terminal bank, means being provided for determining the direction of movement of the wipers in accordance with the position of the calling-subscriber's terminals. The invention is described in connexion with two co-ordinate finders comprising main and brush-choosing switches which operate under the control of units and tens guide-wires, two of which are grounded by the calling-subscriber's line relay. Since the two switches execute their movements simultaneously, the maximum time required for finding a calling line is the time occupied by a switch in taking five steps. Different finders are put in action to deal with successive calls by means of a pilot relay con. trolling a starting-circuit which extends through off-normal contacts to the first idle finder. Construction of switches. A construction suitable for the main switch of a finder is shown in Fig. 2, the brush-choosing switch being similar. The shaft S can be driven in either direction by energizing solenoids e1, e2, which cause a plate d to be attracted against disks d1, d2 on a driving - shaft s1. According to the direction in which the shaft S is turned, one or other of two off-normal contacts c1, c2 is closed by a plate ds having a pin which works in an inclined slot of a plate d3. An offnormal switch OS of ordinary type is also provided. In the system shown in Figs. 3 to 6, the reversible driving-mechanisms of the call-finder are assumed to be of ratchet type. The connector, Fig. 6, is a Strowger switch. Call-finder, Figs. 3, 4, and 5. The brush-choosing switch of a call-finder F, is shown at W<1>, Fig. 4, the main switch being represented by the sets of brushes wa<0>, wb<0>, wc<0>; wa<1>, wb<1>, wc<1> ; &c. The test wipers ws, wp of these switches appear in Fig. 3. The energization of the line relay l59, Fig. 3, of a calling subscriber S59 energizes relays m2, m<1>2 which control the clockwise-movement magnets E2, E<1>2, Fig. 4, of the brush-choosing and main switches. (If the subscriber S04, for instance, had originated a call, the relays m1, m<1>1 controlling the counterclockwise magnets E1, E<1>1 would have been energized.) The relay l59 also grounds the tens guide-wire 5<1> and the units guide-wire 9, and energizes a starting-relay FS. This relay opens the circuit 111 to prevent the energization of a second line relay while the first calling line is being found, and sends a starting-impulse in a circuit st by its contact 117, which is momentarily closed during the forward movement of the armature 116. The starting-impulse energizes the preselected magnets E2, E<1>2, which tension the springs of the operating-pawls so as to move the main and brush-choosing switches from normal in a clockwise direction when the impulse ceases. The off-normal switch OSI, Fig. 5, extends the starting-circuit st to the next idle finder F2 and connects the magnets E2, E<1>2 to an interrupter 133. The main and brush-choosing switches continue their movements until the circuits of the magnets E2, E<1>2 are opened by the test re'ays tp, sp, which are energized when the test wipers wp, ws arrive on the contacts of the grounded guide-wires. The calling line is now connected through the brushes wa<5>, wb<5> of the main switch and through the brush-choosing switch W<1> to the line a, b, and a circuit is closed for a relay CR<1>, Fig. 5, which connects the line a, b to the connector, Fig. 6. The relay CR<1> locks itself in a circuit including in one branch a relay 155, Fig. 6, and in another branch the subscriber's cut-off relay co59. The relay co59 de-energizes the relays l59, FS, m2, m'a, so that a second call in the same group of subscribers can now be dealt with by the next idle finder F2. Connector, Fig. 6. The line relay LR is energized in series with the calling line and energizes a relay RR, which remains energized until the connexion is released, the momentary short-circuitings caused by the line relay closing its back contact 175, in response to the numerical sets of line interruptions, being insufficient to de-energize it. At the first interruption of the tens series, a relay CR is energized in series with the relay RR, and as long as the interruptions continue, this relay remains energized, the intermittent momentary short-circuitings at the front contact 176 of the line relay being insufficient to de-energize it. Each interruption energizes the vertical magnet VM. At the conclusion of the series, the relay CR de-energizes and completes the circuit of the magnet S'M, which moves the side-switch arms 178, 179 to their second position. The units interruptions now operate the rotary magnet RM, and the side switch then moves to its third position, completing the circuit of the test relay 190. Busy test ; supply of ringing-current. If the wanted line is idle, the relay 190 becomes energized and connects up the ringing-macbine R<1>M. When the called subscriber replies, a relay R'R in the ringing-circuit responds to the increased current and energizes a ringing cut-off relay 193, which locks itself up and comp'etes the talking-connexion. Both lines are now supplied with current through the line relay LR. Release. When the subscribers have both hung up their instruments, the relay LR de-energizes and short-circuits the relay RR, which energizes the magnet Rel. This magnet releases the connector, short-circuits the relay CR<1>, Fig. 5, and energizes the relay rl, which locks itself up through the off-normal switch OS1. The de-energization of the relay CR<1> connects the interrupter 133 to the magnets E2, E<1>2 the circuits of which are completed through the contacts c2, c<1>2 of the off - normal switches DS1, DS2. The main and brush-choosing switches of the finder F1 are therefore moved in the same direction as before until they regain their normal position.