Patent GB-178845-A (GB)
Title: Improvements in and relating to automatic traffic distribution for telephone systems
IPC: H04M3/523
Filed: 1922-04-19
Abstract: 178,845. Compagnie Franþaise pour l'Exploitation des ProcÚdÚs Thomson-Houston. April 19, 1920, [Convention date]. Void [Published under Sect. 91 of the Act]. Manual exchange systems; metering systems. -In a system for automatically distributing incoming calls amongst the exchange operators, the first calls are onlv allotted to operators having no call in hand. When each operator has one call in hand, one waiting call is allotted to each operator's position, and when each operator has one call in hand and one waiting, a second waiting call is allotted to each position. When each operator has one call in hand and two waiting, the whole section of the exchange is marked busy. The invention is described with reference to a system in which an incoming call is connected by a preliminary selector to an idle cord-circuit, and an operator's cord-finder then hunts for the selected cord. The cord-circuits at each operator's position are arranged in three groups and a series of relays is employed which, when the first call is allotted to an operator, marks busy all the cords in all the groups of that operator. When every operator has a call in hand, the relays free those two of the three groups which do not contain the busy cord; and as soon as a second cord is seized for the first waiting call both of these groups are again marked busy until each operator has one waiting call when the third group containing neither of the selected cords is rendered idle to receive a second waiting call. The operation of the system will first be described when at least one of the operators is idle. When the calling subscriber A, Fig. 1, removes his receiver, the brushes 11, 12, 13, 14, of the preliminary selector hunt in known manner for an idle cord-circuit. When the test brush 14 reaches the test terminal of an idle cord B the cut-off relay 9 energizes in series with the rotary magnet 10. Relay 24 energizes to supply a holding earth for the relay 9 over the test wire 18 before the slow-release line relay 8 has fallen back. The relay 24 energizes the relay 61 at the operator's position C to close the circuit of the relay 73 of the operator's cordfinder, and also disconnects earth from the wire 48, thus putting a selectable potential upon the test terminal of the cord B in the bank of the cord-finder. The relay 61 breaks the circuits of the relays 104, 105, 106 which are normally energized over a contact 130 controlled by the operator's speaking set, thus marking busy in the banks of the preliminary selector all the operator's cord-circuits. The relay 61 also lights the group lamp 97 and de-energizes the relay 113, the function of which is described later. The relay 73 prepares the circuit for the relay 74 and connects the rotary magnet 80 to the test brush 84; and the cord-finder rotates until the selected cord B is reached. Relay 74 now energizes and (1) energizes the operator's meter 81 to record the call; (2) lights the cord individual lamp L1; (3) connects the calling subscriber to the operator's speaking set over a circuit through the cord B, leads 49, 51, brushes 82, 83, and armatures 78, 79 and 87, 88; and (4) completes an alternating current circuit through the coil 129 so that the calling subscriber and the operator are informed bv induction that they are in communication. The operator enquires the wanted number and tests the wanted line A<1> by touching the tip of the plug upon the sleeve of the jack. If the line is busy, a circuit 34, 59 is completed, giving a busy signal in a winding of the induction coil of the operator's instruments. If the wanted line is idle, she inserts the plug which energizes the relay 33 in series with the called subscriber's cut-off relay 46. Ringing current is supplied over a circuit 32, 37, 39, 38, 34, 28 and one winding of the relay 27 which does not yet energize. An induced current in the other winding of the relay 27 informs the calling subscriber that ringing is in operation. When the called subscriber replies, the relay 27 locks up and completes the talking connection, the calling subscriber's meter 47 being operated over a circuit 29, K3, 17, 13, 5. When the relay 33 energized, the relay 61 was released and the relays 104, 105, 106, 113 energized, thus rendering the remaining cord-circuits at the operator's position idle. The cord-finder was also returned to normal. During the conversation either subscriber may attract the operator's attention by operating his switch hook, thus flashing the supervision lamps L3, L4. The operator may call the calling subscriber by depressing a key K, or may break in on the conversation by means of a key K1, her speaking set being then disconnected from the cord-finder brushes 82, 83 by the relay 86. When both subscribers hang up, the supervision lamps L3, L4 and the pilot lamp 95 are lit and the operator releases the connection in known manner. In order to ascertain whether a calling subscriber is entitled to the connection required, a tone signal may be given from a coil 155 to a coil in the operator's speaking set by depressing keys K2 and K5. Extra units may be recorded on the subscriber's meter 47 by operating the key K3. The key K2 when depressed alone is used when a cord is faulty to mark the test lead 18 busy. When each operator has a call in hand, one of the relays 113, 114, 115 at each operator's position is de-energized and the common relay 126 energizes all the relays 107 individual to the operators. Each group of cords is controlled by one of the relays 104, 105, 106 and when the relay 107 energizes, the two relays 105, 106 are connected to the earth 130 independently of the operated relay 61 so that these two relays energize and the two groups of cords are marked idle to receive a waiting call. When each operator has one call in hand and one waiting, two of the relays 113, 114, 115 at each position are de-energized and the common relay 127 operates to energize relays 108 by which one of the relays 104, 105, 106 is energized independently of those two of the relays 61, 62, 63 which are energized, and the 'third group of cords is marked idle to receive a second waiting call. When each operator has one call in hand and two waiting, all the relays 113, 114, 115 at all the positions are de-energized to light the overseer's signal lamp 128. If an operator vacates her position, she opens her talking-circuit which opens the contact 130, de-energizing all the relays 104, 105, 106, 113, 114, 115 and marking the whole position busy. In a modified cord-circuit, Fig. 2, the intermittent flashing of the lamp L4 in order to attract the operator's attention is automatically started and continued when the calling subscriber momentarily replaces his receiver. The momentary de-energization of the relay 211 energizes the slow-release relay 203 which locks up over a contact of the key K1 and completes the circuit of the lamp L4 in series with an interrupter. The operation of the listening-key K1 extinguishes the lamp L4 and restores the relay 203. When both subscribers hang up, relays 211, 212, 207 relapse and energize relay 203 which lights the lamp L4 continuously in a circuit 222, 209, 206, 201, 60. In a further modified cord-circuit B2, Fig. 3, release is controlled by the calling subscriber alone. When the cord is seized the relay 315 energizes a relay 308 which prepares the circuit of the lamp L4, short-circuits a relay 304 and prepares the circuit of the relay 327 which is energized when the plug is inserted. During conversation the lamp L4 may be intermittently illuminated by the calling subscriber operating his switchhook. At the end of conversation when the calling subscriber hangs up, relay 315 relapses and de-energizes relay 308, removing the short-circuit from the relay 304 which energizes in series with relay 327 and the called subscriber's cutoff relay 46. The two latter relays fall back owing to the resistance of relav 304, thus releasing the called subscriber. Relay 304 closes circuits for the lamp L4 over the armature 301 and for the lamp L3 in a circuit 302, 317, 319, and the operator seeing both lamps illuminated, takes down the plug.