Patent GB-658514-A (GB)
Title: Automatic telegraph exchange systems
IPC: H04L12/00
Filed: 1947-12-30
Abstract: 658,514. Telegraph exchange systems. STAATSBEDRIJF DER POSTERIJEN TELEGRAFIE EN TELEFONIE. Dec. 30, 1947, No. 34837. Convention date, Dec. 18, 1942. [Class 40 (iii)] In an automatic telegraph exchange system in which the signals employed to effect the connection between subscribers of the same or different exchanges are transmitted in the same code as that employed for the telegraphic traffic a supervisory relay in the connecting circuit in the exchange of the calling subscriber is operated if signals forming part of a message are transmitted by the calling subscriber after the selecting signals, but before the establishment of the connection, and its operation breaks down the connection of the calling subscriber to the exchange. The connection is also broken down by the operation of a further supervisory relay in response to signals other than numerals and predetermined auxiliary selecting signals. During the normal rest condition a small current, e.g. 5 milliamps, flows over the line wires 1a, 1b and a polarized receiving relay ER at the subscriber station. The initiation of a call by the closure of a key OT short circuits a resistance W1 so that the line current is greatly increased, e.g. to 50 milliamps. Line relay LR at the exchange is operated, but relay ER is not affected. At contact lr1 test voltage is applied to the wiper d of a line finger of a free junction circuit, and at contact lr2 start relay KS is operated. At contact KS1 the driving magnet KK is energized, and when a free junction is found relay KC operates over contact KS2 and locks up over contact KC and low resistance winding of a relay KH. The circuit of magnet KK is broken and the potential at the junction point of contacts h1, h2 is reduced so that relay KS releases. Connection of subscriber line to a free register (Fig. 3). The closure of contacts kh1, kh3 operates start relay RS which at contact rs1 closes the circuit of the driving magnet RK of the line finder KZ. When a free register has been found, relay RC operates over the abank and looks up over a low resistance winding and a slow-release relay RH. A free register will be such that contacts z, y and z are all closed and a circuit will be completed over contacts sp1, hk1, z, y, x, relay RB, b-bank, contacts kv2, kd3, kh2, relay KB to battery. At contacts rb3, rb4 the junction circuit is connected to a free register comprising groups of five relays on which the five-unit signals are set up and stored. At the junction circuit the contacts kb1, kb2 connect the register to the wipers a, b. At kb7 relay LA is energized and at contact kb6 a circuit is completed over relays A, LB. At contact kb3 the relay COR is operated extending the line to the calling subscriber at contact cor1, and at contact cor2 reversing the current flow over the subsciber's circuit so that relay ER, Fig. 1, operates. Relay H is operated and at contacts h2, h3 closes the circuit of the motor MA indicating that the transmission of the selecting signals can begin. Transmission of calling signal and supervisory arrangements. The number of the called subscriber is prefixed by " figures " and is followed by the code combination for the " + " sign. The code combinations are passed to a checking circuit, Fig. 5. A sequence switch operated by the register moves a contact from the position shown so that the " figures " combination operating contacts oa1, ob2, od1, oe1 completes a circuit over a winding of a relay CF and over the left-hand winding of a relay SP which also has its righthand winding energized over contacts e, p2, sp2. The operation of the relay CF releases the sequence switch for registration of the subsequent signals. The contact hb is moved to the position shown and the operation of the appropriate contacts oa1 ... oe4 corresponding to the numerals 0 ... 9 completes a circuit for the left-hand winding of relay SP which remains unoperated. After the registration of the required number, the sequence switch closes the left-hand contact hd and the " + " signal, having marks for the first and fifth code element, operates contacts oa1, oe1 so that a circuit is completed over relay P and the left-hand winding of relay SP. If the selecting signals included a signal other than "figures," a numeral or the " + " signal, relay SP operates and at contact sp1, Fig. 3, opens the circuit of relays RB, KB which release and break down the connection by de-energizing relay COR and restoring the subscriber's circuit to normal. Extension of calling circuit to the called subscriber. When relay P operates in response to the " + " signal, a circuit is completed from the register to the group selector, and at contacts p3, p4 the circuit is extended towards the called subscriber. When the line selectors are set into operation relay k<SP>1</SP>s operates and at contact k<SP>1</SP>s3 prepares a circuit for a supervisory relay KV. When the desired connection has been established relay kd operates and at contact kd3 releases the selector associating the junction circuit with the register. At contacts kd2, kd4 the connection between the subscribers' lines and the register is broken and at contacts kd1, kd5 the telegraphic circuit between the subscribers is completed. Additional supervisory arrangement. If, after sending the number of the desired subscriber followed by the " + " sign, the calling operator transmits any signal, a circuit is completed for the relay KV by the first transit of the armature a of the relay A. Relay KV operates, locks up temporarily over contacts kv1, kb5 and at contact kv2 opens the circuit of the relays KB, RB which release and breaks down the calling circuit. Called subscriber busy. If the called line is engaged, a relay HK (not shown) is energized, and at contact hkl opens the circuit of the relays RB, KB which break down the connection.