Patent GB-211231-A (GB)
Abstract: 211,231. Relay Automatic Telephone Co., Ltd., and Johnson, B. B. Nov. 17, 1922. Automatic exchange systems; party-line systems. - A party-line system having normally say, four stations on each line, is arranged so that if a subscriber removes to another district he may be transferred to another party line without any change in his number, whilst if a number becomes dead, a new subscriber having a different number may be accommodated at the vacant position, a call to the dead number resulting in the calling subscriber either being connected to an operator's position or being given a distinctive tone signal. The system can thus continue to be worked at its full capacity in spite of such removals and transfers of subscribers and without any inconvenient renumbering of the parties transferred. The invention is described with reference to a system in which connections are established entirely by relays. A calling subscriber becomes connected in known manner to a connecting circuit, Fig. 1 (Prov.) having associated therewith a relay group, Fig. 2, which selects an idle impulse-responder, Figs. 3<a> - - 3<d>, the latter operating to pick out marking-circuits in the manner fully described in Specification 181,119. An extra digit 1, 2, 3 or 4 is inserted in the number of each party-line subscriber between the hundreds and tens digits; thus, the subscribers on line 200 are numbered 2100, 2200, 2300, 2400, a separate marking-wire from the impulse-responder being assigned to ,each subscriber. The extra digit causes the energization of one of the relays PYM1 - -PYM4 in the " marker," Fig. 4, to control two relays FS1, FS2, Fig. 5, which by their energization together or singly or by their non-energization connect up the particular one of the four ringing leads 32, 33, 37<a>, 38 which is appropriate to the wanted subscriber. If a vacancy on a line is filled by another subscriber wishing to retain his present number, no modification of the ringing- control apparatus will be required as long as the second digit of his number is different from the second digit of the other numbers already on the line, but if the second digit is the same as one already in use, the marking-wire of the transferred subscriber is modified by the insertion of a relay FC, Fig. 8, which prevents the transmission of the normal ringing current associated with the particular second digit and replaces it by the fourth ringing current which is not otherwise in use on the line. When the marking circuits have been completed, the connecting circuit, Fig. 1 (Prov.), is connected in the manner described in Specification 181,120 to the ringing group, Fig. 5, and thence to the marked subscriber's unit, Fig. 7. In the arrangement in which a subscriber calling a dead number is connected to an operator's position, the marking-wire corresponding to the dead number leads to a relay JME, Fig. 6<a>, directly controlling the connection to the operator, it being therefore unnecessary for the operator's apparatus to be responsive to any particular ringing- current. The manner in which the various figures are to be arranged relatively to one another to form the complete system is shown in Fig. 1 (Comp.). In the following detailed description it will be assumed that a call is being made to party line subscriber No. 2100. Connection to wanted line. The extension of the calling line to the connecting circuit, Fig. 1 (Prov.), causes the energization of relays I, G, GX, the latter completing circuit 51 for relay BB, and circuit 6 for relay FI, Fig. 2, which locks up in a simplex circuit 4. Relay RC1 energizing in circuit 7 connects the calling line over leads A3, B3 to the first idle impulse-responder, Figs 3<a> - - 3<d>. Negative battery, connected by relay PF to the conductors shown in heavy dotted lines, energizes all relays BK, Fig. 3<b>, which complete a circuit 9 in which relay DM1, Fig. 3d, operates. Relay MK1 operates in circuit 10 and disconnects relay BK1. At the end of the first digit (two impulses) relay BK2 is de-energized, relay DC1 is energized and a circuit 11 is completed in which relay HD 2.7 operates, locks up and breaks circuits 9, 10 causing relay DM1 to fall back and extend circuit 9 over circuit 12 to operate relay DMP. The next two digits in a similar manner cause the locking up of relays PY 1.6, TN 5.0, respectively (the latter in combination with relay TN 6<c>), after which circuit 9 is extended over circuit 19 to operate relay DM 3. At the end of the final digit (ten impulses), relay DC 1 completes circuit 20 for relay MC1 which closes the following marking circuits : (1) circuit 21 for a relay PYM1 which corresponds to the particular station on the party line and controls the transmission of the proper ringing current; (2) circuit 22 for hundreds marking relay HDM 21; (3) circuit 23 for tens marking relay TNM 210; (4) circuit 24 to energize relay OTM1 which marks the calling circuit, Fig. 1 (Prov.), in the relay connecting group, Fig. 6; and (5) circuit 25 leading to the test circuit of the wanted line, Fig. 7. The connecting-circuit, Fig. 1 (Prov.) is connected over the relay group, Fig. 6, in the manner described in Specification 181,120, to the ringing group, Fig. 5, at which relay ITM energizes. The usual holding circuit 27 includes a relay ITB which disconnects relay ITM and completes circuit 29 for ringing-relay RG. Party-line ringing. Relay RG connects ring- ing lead 32 over circuit 31 to the called subscriber. If the call had been to one of the other stations 2200, 2300, 2400 on the same line, the corresponding energization of relay PYM2, PYM3 or PYM4 would have energized relays FS1 (in circuit 34a), FS<2>, either separately or together and thus have connected up one of the other ringing leads 33, 37<a>, 38 respectively. Replacement of one of the normal party-line subscribers by another subscriber having a different number, the second digit of which is different from the second digit of all the other parties on the line. In this case, no modification of the ringing-control apparatus is necessary since the different PYM relays will be energized for the different subscribers and control the transmission of different ringing-currents as described above. The provision of a separate marking circuit for each subscriber permits subscribers, whose numbers may have different hunderds, tens or units digits, to be accommodated on the same party line without difficulty. Replacement of one of the normal subscribers by a subscriber having a different number, the second digit of which is the same as that of one of the other subscribers. For example, suppose that subscriber No. 2290 is added to a line to which subscribers 2100, 2200, 2300 are already connected. Calls to subscriber 2200 operate relay PYM2 and current from ringing lead 33 is transmitted as described above. The marking- lead 25<b>, Fig. 4, of subscriber 2290, however, is connected in series with a relay FC4, Fig. 8, which breaks circuit 34<a> to prevent the transmission of the normal signalling current from lead 33 and completes circuits 35, 37 for relays FS1, FS2, to connect up the fourth ringing lead 38 corresponding to the spare second digit 4. Completion of talking connection at connecting-circuit, Fig. 1 (Prov.), in the case of a successful call. The operation of relay RG, Fig. 5, completes circuit 50 through the lower winding of relay IS which energizes to close circuit 53 for relay ICO, the operation which opens the circuit of relay BB and extends circuit 50 over circuit 50a to energize relay B2. When the called subscriber replies, relay RT, Fig. 5, energizes and removes the short.-circuit around relay RTX which opens circuit 29, the sluggish release of relay RG permitting the successive closing of circuit 50<b> to short-circuit relay B2, and circuit 29b to energize relay S1. Relay S1 closes circuit 50<c> for relay S2 and relay ME energizes in circuit 54 and completes the talking connection over the heavy conductors, including the repeating coils, microphone current being supplied over relays B1, B2. Transmission of special tone signal to calling subscriber in case of a call to a dead number. If no marking circuit 25 is completed, differential relay SU, Fig. 3<a>, energizes over its right-hand winding and disconnects lead B3 from relay De1, causing the energization of relay IS over its upper winding. Relay ICO operates as before in circuit 53. Since, at this time, relay B2 is not operated, relay S1 operates in circuit 55<a> and, before relay BB releases, relay RR operates in circuit 56. Upon the release of relay BB, tone signal NU is connected up and transmitted to the calling subscriber. Connection to operator's position in case of a call to a dead number. The marking lead 25 corresponding to a number no longer in use as a party-line number is extended over circuit 52 to a relay JME, Fig. 6<a>, which operates in known manner to connect the calling trunk A<a>, Fig. 6, to an operator's line E2a,Fig. 6<a>. Specification 181,117 also is referred to.