Patent GB-190322440-A (GB)
Title: Improvements in or relating to Telephone Systems
Inventor: FAIRWEATHER WALLACE CRANSTON
Filed: 1903-10-17
Granted: 1904-10-13
Abstract: 22,440. Fairweather, W. C., [Kellogg Switchboard and Supply Co.]. Oct. 17. Telephone systems; telephone calls. - Relates to telephone systems, a n d more particularly to central battery systems. In the arrangement shown in Fig. 1. the line wires 2, 3 are bridged at the subscriber's station bv the call bell 4 and condenser 5. J, J<2> represent jacks on the multiple board. When the subscriber lifts the receiver 7 from the hook, the circuit of the common battery B (one terminal of which is earthed) is closed through the wire 10, line relay R<2>, line 2, 3, cut-off relay R, and earth. The relay R does not respond to the weak current through the line, but the relay R<2> closes the circuit of the lamp S, which indicates the call. The operator inserts the answering plug P of her cord circuit into the jack J<2>, thus completing a local circuit through the supervisory relay r<2>, sleeve strand and conductor, and relay R. The circuit of the relay R<2> is consequently broken, and the lamp S extinguished. Owing to the closed circuit 2, 3, the supervisory relay r is energized, and the supervisory lamp S' is prevented from lighting up. The operator's microphone, induction coil, and receiver are indicated at 13, 12, 11, c<3> being a condenser. Having ascertained the number of the subscriber wanted, the operator tests in the usual way with the tip of the calling plug P<2>, which is normallv to earth through the relay r<3>. If the line is engaged, the test rings are connected to the live pole of the battery, and the consequent current to earth disturbs the potential at the terminals of the condenser c<3> in the operator's bridge, and produces a click. If the line is free, the calling plug P<2> is inserted and the ringing-key 16 operated, and the generator 14 sends current to line, the circuit being completed through wire 17 and battery B. Current from the battery flows through the cut-off relay R of the called line to keep the line signal inoperative during ringing. After the subscriber has been called, and before his response, the supervisory lamp S<3> is lighted owing to the circuit established through the relay r<4> and the cut-off relay R of the called line. When the subscriber responds, however, the closing of the metallic line circuit brings the relay r<3> into action, and the lamp S<3> is extinguished. Daring conversation, the battery B furnishes the required currents in the lines, and the voice currents are repeated through the condensers c, c<2>. When the receivers are returned to their hooks, the relays r, r<3> are independently de-energized, and the supervisory lamps light up, indicating to the operator that the conversation is finished. The relay R may be wound with a high-resistance as well as a lowresistance coil, the high-resistance coil being automatically thrown in when the plug is inserted and the relay becomes effective. Two batteries may be used, supplying current independently to the subscriber's lines. The cord circuit may have the strands transposed, the sleeve of the answering plug being connected to the tip of the calling plug, with the view of balancing the lines as regards the earth connections through the cut-off relays R. A third relay may be used in conjunction with the relays R, R<2>. It is of low resistance, and is placed in the line circuit, and is only energized when the answering plug P is inserted in the jack. It then cuts out both the other relays, and removes all ground connection from the line. Instead of the action of this third relay being dependent on the strength of the current, the relay may be of the polarized type, the current when the subscriber is calling being opposite in direction to that which passes, in the line when the answering plug is inserted. This arrangement is shown in Fig. 4. The relay R may be polarized, a battery weaker than B, and oppositely connected, being used to supply the current when the subscriber calls, such current failing to actuate the relay R. When the answering jack is inserted, the main battery overcomes the other, and the relay R opens the circuit of the relay R<2>. Fig. 6 shows two subscribers' stations on a party line 2, 3, repeating coils W<2> being used between line and switchboard. A battery B, which may be the same as the central battery, is placed in the line, and the removal of any receiver 7 from its hook energizes the relay R<4> and closes the circuit of the line signal lamp through the wires 26, 27, contact springs 22, 21, and earth. When the answering plug P is inserted in the jack J, the cut-off relay R is energized through the earth contact 29, and the line signal lamp is extinguished. The supervisory relays r<5>, r<6> are wound differentially, and the currents flowing through the strands s, t, jack springs, and switchboard side of the repeating coils fail to energize them, but when a subscriber hangs up his receiver the relay R<4> is de-energized and an unbalanced current flows through the strand s, sleeve spring, repeating coils contact 22 to earth. The supervisory lamp S<2> then lights up, indicating that the conversation is over. A similar arrangement is described in which the repeating coils W' are dispensed with. In another modification, both jack springs are normally disconnected from the line wires, being connected thereto by the cut-off relay, through which the battery current is supplied to the line. In a further modification, high-resistance impedance-coils are connected across the strands of the cord circuit for testing purposes. In another system a highimpedance test relay is employed, and where the lines are provided with two parties, one having a bell in a ground branch from one side of the line and the other from the opposite side of the line, a generator is employed, which, by pressing one ringing key, sends ordinary ringing current through the sleeve side of the line to earth, and by pressing a second key sends a pulsating current through the tip side of the line. In the system shown in Fig. 16 the cut-off relay is dispensed with, a retardation coil 65 being placed in a ground connection from the line 3. When the subscriber removes the receiver 7 from the hook, the circuit of the battery B is completed through the line relay R', line 2, 3, and coil 65, the lamp S being then lighted. When the answering plug P is inserted in the jack J<2>, the supervisory relay r shunts the relay R', of higher resistance, and puts it out of action, extinguishing the lamp S. When the receiver is returned to the hook, the relay r is de-energized, but the circuit of the relay r<2> remains closed through the coil 65, and the supervisory lamp S<2> lights up. The relay r' is provided with an extra set of contacts serving alternatively to complete the tip strand t<2> for talking, and, (normally), to connect the forward portion of the strand with a conductor leading to the high-resistance and highimpedance test relay r<11>. A " consequent pole " relay is employed in one modification. Two cores, with windings of high and low resistance respectively but with equal numbers of turns, are united by yokes forming a closed magnetic circuit. When the subscriber calls, the same current flows through both windings, and a consequent pole is produced at the centre of the yoke with which the relaytongue co-operates, the tongue being attracted to close the circuit of the signal lamp. When the call is answered, the high-resistance winding is shunted by a low-resistance supervisory relay, and the consequent pole disappears, the magnetic circuit of the other coil being closed. In another modification, the line and cut-off relays are united into a two-core relay the poles of which act oppositely on an armature pivoted centrally. Numerous modifications are described involving rearrangement of the relays and line and supervisory signal lamps, and of the operator's testing and calling apparatus, including, in particular, the testing relays. Fig. 33 shows a trunking system in which the signal receiving and sending apparatus of the usual cord connectors may be employed equally well when connection is to be made through the trunk line, as when connection is made directly between two telephone lines. L represents the subscriber's station, R<2> the line relay, R the cutoff relay, and S the calling lamp. The operator at the station X to which the subscriber is connected inserts the answering plug P in the subscriber's jack and bridges her receiver circuit across the cord circuit, the speaking taking place through the repeating coils w, w<2> and w<3>, w<4>. The supervisory signal magnet r<20> is energized. Having ascertained that a subscriber at another office is wanted, the order circuit 108 is employed to communicate with the operator at that office and ascertain which trunk line is to be used. The calling plug P<2> is then inserted in the jack J of that trunk line, and the operator at the distant station inserts the plug P<3> in the jack of the subscriber wanted. The call is made by the operator at station X, the circuit of the generator 105 being completed through the strand t<3>, the called subscriber's line, strand s<3>, repeating coil w<8>, and battery B<3> to the ground. The condenser c<4> does not appreciably shunt the low frequency calling current. When the called subscriber lifts his receiver from the hook, current from the battery B<3> flows through the repeating coil w<8> and through his line, returning by the strands t3, t<2> and supervisory signal r<21> to the ground. The operator at station X is thus notified of the called subscriber's response. The circuit of the ''disconnect signal S<4>, although closed at 107 by the removal of the plug P<3> from its seat, is maintained open by the energized relay r<23>. When the subscribers return their receivers to the hooks, the signal magnets r<20>, r<21> are de-energized, indicating to the operator at station X that the conversation is over. The withdrawal of the