Patent GB-193073-A (GB)
Title: Improvements in or relating to party-line telephone systems
IPC: H04Q5/00
Filed: 1921-08-17
Abstract: 193,073. Hastings, R. C. M. Aug. 17, 1921. Party-line systems and apparatus.-In a lockout party-line system with ratchet-operated substation selectors controlled by impulses from an exchange, and in which a substation may be rung regardless of the position of the switchhook, a contact 85, Figs. 1 and 3, actuated by the shunt contacts 38, 39, may either engage a contact 86 and close an alarm circuit bridged by the switch-hook, or it may bridge the contacts 86, 90 and thereby close an independent alarm circuit. Each selector comprises a disc 36 with two peripheral grooves 54, 58, Fig. 15, coacting with a group of spring contacts 39 - - 85, Fig. 3, which serve to complete the speaking circuits at the calling and wanted substations, and to close a ringing circuit at the latter station, and to short-circuit the instruments at all other substations. Teeth 38<a>, Fig. 5, are placed across both grooves at selective calling positions and a pin 38<1> on the spring 38 rides in one or other of the grooves 54, 58, or beneath the lower edge of the disc, the pin riding through slots in the bounding ridges of the grooves and taking with it the contacts 39 - - 85, which are swingingly mounted. Normally the pin 38<1> rides in the groove 54 at a called station, and when the tooth 38<a> is engaged contacts 85, 86 close a bell-circuit bridged by the hook, but if the called subscriber has not replaced his receiver the pin rides in the groove 58 and when a tooth 38<a> is encountered the contact 85 bridges the contacts 86, 90 and closes an independent bell-circuit. Exchange circuits and apparatus.-These are shown at the right of Fig. 1, and comprise an impulse transmitter K adapted to send a definite number of impulses, a calling plug 2 for insertion into calling jacks 17, and an answering plug 1 for insertion in an answering jack 14, all of the type described in Specification 9986/13 and arranged and operating as therein described. Party-line substation circuits; selector and lock-out arrangements. The circuits of a single substation on a party-line L, L<1> are shown at the left of Fig. 1. The step-by-step selector 36, 37 is operated by a magnet 29 in the line wire L'. The substation circuit is adapted to be shortcircuited by a pair of lock-out contacts 38, 39 operated by the selector. The transmitter T and the primary of the transformer 68 are in a local battery circuit which includes the upper switchhook contacts 49, 50 and contacts 70, 71, which are only closed when the lock-out contacts 38, 39 are open. Contacts 85, 86, 90, belonging to the same group as contacts 38, 39, 70, 71, control the circuit of the call bell 81, the contacts 86, 90 being arranged one above the other so that if the pin 38<1>, Fig. 15, is passing in the groove 54 the contacts 85 and 86 engage when a tooth 38<a> is reached, whilst if the pin is passing in the groove 58 the contacts 86, 90 are bridged by the contact 85. The contacts 38, 39, 70, 71, 85, 86, 90 are controlled by a pin 38<1>, Fig. 15, which is carried by the contact 38 and engages in either of the grooves 54, 58 in the edge of the disc 36. Normally the pin 38<1> is held below the ridge a, which projects slightly more than either of the ridges b or c, and holds the contacts 38, 39 open and the transmitter contacts 70, 71 closed. When the pin 38' is in either of the grooves 54, 58 the lock-out contacts 38, 39 are closed, while the transmitter contacts 70, 71 and bell contacts 85, 86, and 90 are open except when a tooth 38<a> is engaged. The group of contacts 38, 39, 70, 71, 85 is pivotally mounted at 40, Fig. 3, so as to be able to swing across the periphery of the disc 36, this movement being possible when the pin 38<1> is opposite slots 55, 55', or 57 in the ridges a, b, and being determined by the energization or non- energization of a magnet 47. Thus if the pin 38<1> is below the ridge a and the magnet 47 is not energized when the slot 55<1> passes the pin the tension of a spring 41', Fig. 3, causes the pin to pass into the groove 54, and if the, pin 38<1> is in the groove 58 and the magnet 47 is energized when the slot 57 passes the pin, the magnet 47 overcomes the tension of the spring 41<1> and the pin passes through the slots 57, 55. The magnet 47 is energized, under conditions described later, by movement of the switch-hook 25 and by contacts closed by pins 37<1> on the disc 37. The switch-hook 25 is normally looked in its depressed position by the armature 168 of a magnet 169, but is adapted to be released electrically at the calling substation by the energization of the magnet 169, or mechanically at the called station by pins 172 (on the disc 37) which engage the armature 168. All the pins, slots, &c. are repeated three times around the circumference of the discs 36, 37, it being arranged that a movement of 120 degrees from the normal position brings the selector to another normal position. Calling the exchange operator. The receiver is removed at the calling station and the magnet A is operated, thereby signalling the operator by means of a call signal 9 or a night-bell 174 energized by a generator G. Actuation of the magnets A also energizes the magnet 169 which releases the switch-hook lock. Selection of wanted party-line substation. The operator, after inserting the plug 1 in the answering jack 14, enquires the number of the wanted party-line subscriber and transmits a series of impulses as described in the before-mentioned Specification. The impulses energize the magnets 29 of all the substations in series, to rotate the selectors. The pin 38<1> at all substations is normally below the tooth 60, Fig. 5, forming part of the ridge a, but it now travels from right to left (actually it is the disc 36 that moves), and at all substations except that at which the call originated the pin, under tension of the spring 41<1>, Fig. 3, passes through the slot 55<1> into the groove 54, closing contacts 38, 39 to short-circuit. the substation instruments. At the calling station, however, the receiver being off the hook, the magnet 47 is energized, at the moment the pin passes the slot 55', in a circuit including the contacts 44, 45, closed by a pin 37<1> on the disc 37, switch-hook contacts 61, 62, and battery 65, and holds the pin 38<1> below the ridge a, so that the instruments at this substation remain in the speaking condition. The impulses advance the selectors to such a position that the pin 38<1> at the wanted substation is brought on to the tooth 38<a>, operating the group of contacts 38 - - 90, so that at this station also the instruments are in speaking condition and a local circuit is closed over contacts 77, 78, 85, 86 for the call-bell 81. At the same time a pin on the disc 37 releases the switch-hook lock. When the called subscriber answers the call the ringing circuit is opened at switch-hook contacts 77, 78. Restoration of party-line selectors after conversation. This is effected when the remaining impulses of the cycle are transmitted as described in the before-mentioned Specification to step forward the substation selectors to the next normal position. At the calling station the pin 38<1> travels below the ridge a, and at the moment it arrives below the slot 55, contacts 74, 75 are closed by a pin 37<1> on the disc 37, so that if the receiver has been replaced the magnet 47 is energized in a circuit including the contacts 74, 75, 77, 78, and holds depressed the pin 38<1>, which is restored to its normal position beneath the tooth 60. At the called station the pin 38<1> travels in the groove 54, and if the receiver has been replaced, at the moment it arrives above the slot 55, the magnet 47 is energized as at the calling station and the pin 38<1> is restored to the normal position 60. Operation when a subscriber fails to hang up his receiver. If the receiver had been left off the hook at either substation, the contacts 77, 78 are open and the magnet 47 is not energized when the pin 38' passes the slots 55, 57 so that the pin is moved by the tension of the spring 41<1> into the groove 58 when it comes to rest. At the calling station the pin 38<1> passes through both slots 55, 57, but at the called station, being already in the groove 54, it only passes through the slot 57. The fact that the receiver is off the hook at a particular substation does not prevent that substation from being selected and called by the exchange, since the pin 38<1> in such a case travels in the groove 58 to a tooth 38<a>, and the call-bell is rung over the contacts 85, 90, bridged by the contact 85. Means are provided whereby a subscriber who has omitted to replace his receiver may, by depressing the switchhook, trip the pin 38<1> from the groove 58 to a. position beneath the ridge a, in order to make a call to the exchange. For this purpose the base of the switch-hook rod 25<1> is formed with a wedge-shaped end 25<11>, Fig. 22, which engages the end f of an arcuate pawl 86<1>, Fig. 21, on the disc 36, the pawl, which is slidingly mounted, thereby moving so that its other end d depresses the contact 38 and trips the pin 38<1> below the ridge a. The end f of the pawl 86<1> is pivoted for lateral movement (as shown by dotted lines in Fig. 21) so that any fixed part of the selector engaged during rotation will not slide the pawl. In a modification, Fig. 24, the pin 38<1> is tripped by a lever 86<a> mounted on the disc 36 and adapted to be depressed by an abutment 25<11> on the switch-hook rod 25<1>. Signalling busy condition of party-line to subscribers thereon. This is effected by a lamp 161, Fig. 3, which is energized at contacts 157, 158, which are closed by a segmental ridge 155 on the disc 37, when the selector is off-normal. Recording messages when the called party is absent. The operating magnet P of a telegraphone may be inserted in series with the receiver R, and the starting of the machine controlled by clutch mechanism actuated by a magnet ener