Patent GB-168338-A (GB)
Title: Improvements in or relating to party-line telephone systems
IPC: H04M1/272
Filed: 1920-03-01
Abstract: 168,338. Hastings, R. C. M. March 1, 1920. Party-line systems and apparatus.-In a lockout party-line system, with ratchet-operated substation selectors controlled by impulses from an exchange, the transmission of the proper number of impulses is effected by an operator's keyboard in conjunction with an impulse machine common to the exchange. The depression of a key causes the energization of a corresponding self-locking relay, so that the keys may be of non-locking type. Other features of the system, relating especially to the substation selective and lock-out arrangements, are claimed in Specifications 168,337 and 168,568. Exchange circuits; impulse machine and operator's keyboard. The exchange circuits and apparatus are shown at the right of Fig. 1. The impulse machine K is common to the exchange and can be taken into use by any of the operators, each of whom has a set of keys a<111>, b"', - - k<111>, corresponding in number to the maximum number of parties on a line, and a key n<111> for sending restoring impulses. To send a given number of impulses to line L, L<1> (the plug P or P<1> being in jack J and the cord ringing-key K<1> being thrown) the operator presses one of the keys, such as a<111>, which energizes a corresponding relay 28b over contact d<11> in series with relays 32<a> and 21a and contact 23<a>. Relay 28b locks this circuit so that it is independent of key a<111> and contact 23a, and relay 32<a> energizes magnet 16<a>, which withdraws a catch 15<a> from a notch in a disc 14<a>, allowing the machine K to be rotated by a friction pulley driven by a motor 13<a>. The rotation of the machine K closes an off-normal contact 42<a>, energizing a busy lamp 45<a>, a relay 24<a> which opens contact 23<a> to prevent a second operator from using the machine until it has returned to normal, and a relay 48<a>. A star wheel 19<a>, Figs. 1 and 4, operates contacts 52<a>, 53<a> to send impulses to line from a generator G, the impulse circuit including a relay 59<a> which flashes a tell-tale lamp 74<a>. After a number of impulses corresponding to the key a<111> which was depressed, the contact a<11> parts company with the stepped barrel of the machine K and unlocks the circuit of relays 28b, 32<a>, and 21<a>. Relay 21a opens the impulse circuit and relay 32<a> de-energizes magnet 16<a>, so that the impulse machine is stopped when it regains its normal position. The off-normal contact 42a is then opened, de-energizing relays 24a, 48<a>, so that the impulse machine is rendered available to other operators. Modified exchange circuits, Fig. 2. In this modification the impulse machine K<11> runs continuously, but when a key has been pressed impulses only begin to be sent when the machine next passes through its normal position. The depression of key k<111>, for example, energizes relays 28<d>, 48<b>, which lock up independently of the key. When the machine next passes its normal position, contact 42<b> is closed and energizes relays 21<b>, 28<m> in a circuit which includes contacts 78<b> and k'. Relay 28m unlocks relays 28<d> and 48b and relay 21<b> completes the impulse circuit from contacts 52b, 53b. Relays 21<b> and 28<m> lock up in a circuit including contact k<2>, but independent of contacts 42b, 78b, so that the transmission of impulses is continued, as in Fig. 1, until contact k<2> is opened. Party-line substation circuits; selector and lockout 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 35, 37 is operated by a magnet 29 in the line wire L<1>. The receiver R, in series with the secondary of a transformer 68, is also permanently connected in the circuit L', in parallel with the magnet 29, but is adapted to be short-circuited 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 switch hook contact 61 and contacts 70, 71 which are only closed when the lockout contacts 38, 39 are open. Contacts 85, 86, belonging to the same group as contacts 38 - - 71, control the circuit of the call bell 81. The contacts 38, 39, 70, 71, 85, 86 are controlled by a pin 38<1>, Fig. 15, which is carried by the contact 38 and engages in a groove 58 or 54 in the edge of the disc 36. When the pin 38<1> is in the groove 58 the receiver lock-out contacts 38, 39 are closed, while the transmitter contacts 70, 71 - and bell contacts 85, 86 are open, as shown in Fig. 16. There are, however, in the groove 58 teeth 60<a>, Fig. 8, at the normal positions of the selector, and teeth 38a at selective positions which are different at each station, and when the pin 38<1> is or one of these teeth it opens contacts 38, 39 and closes contacts 70, 71. The tooth 38a also closes tie bell contacts 85, 86, as shown in Fig. 17, but the tooth 60<a> is smaller and leaves these contacts open, as shown in Fig. 18. The groove 54 is shallower than the groove 58, and when the pin 38<1> is in this groove it opens contacts 38, 39 and closes contacts 70, 71, but does not close contacts 85, 86, as shown in Fig. 15. The group of contacts 38, 39, 70, 71, 85 is pivotally mounted so as to be able to swing from the position shown in Fig. 15, to that shown in Fig. 16, or vice-versa. This movement is possible when the pin 38<1> is opposite slots 55<1>, 60 in the ridge b between the grooves, and is determined by the energisation or non-energization of a magnet 47. Thus, if the pin 38<1> is in the groove 58 and if the magnet 47 is energized when the slot 60 passes the pin, the pin will be transferred to the groove 54, or if the pin is in the groove 54 and the magnet 47 is not energized the pin will be transferred to the groove 58 by the retracting-spring of the armature of the magnet 47. The pin can move in either direction through the slot 60, but the slot 55<1> is stepped so that the pin can only move through.it from the groove 54 to groove 58, and not vice-versa. The magnet 47 is energized, under various conditions which will be described later, by the movement of the switch-hook 25<1> and by contacts closed by pins 37' on the selector disc 37. It should be noted that the selector is arranged so that a movement of 120‹ from normal position brings it again to normal, the pin 37<1>, teeth 60<a> and 38<a>, and slots 55<1> and 60 being repeated three times round its circumference, as shown in Fig. 8, which represents a developed view of the circumference of the disc 36. Calling the exchange operator. When the receiver is lifted at a calling substation, ground g<1> is connected through contact 61 to line L<1>, energizing a call signal 9 at the exchange. The signal 9 may also energize a night-bell 174 or buzzer 175. Selection of wanted party-line substation. The operator, after inserting plug P in jack J, enquires the number of the wanted subscriber (who, it will be assumed, is on the same party line) and transmits a series of impulses as described in a previous paragraph. The impulses energize the magnets 29 of all the substations in series to rotate the selectors. The pin 38' at all substations is normally in the groove 54 below the tooth 60<a>, but it now travels (actually it is the disc 36 that moves, but it is convenient to fix attention on the relative movement of the pin) from right to left, Fig. 8, and at all substations except that at which the call originated the pin passes through slot 55<1> into groove 58, closing contacts 38, 39 as shown in Fig. 16 to short-circuit the receiver. At the calling substation, however, the receiver being off the hook, the magnet 47 is energized, at the moment when the pin passes the slot 55', in a circuit including brush. 45, pin 37<1>, contacts 44, 61, wire 66, battery 65, and wire 51', and keeps the pin 38<1> in the groove 54, so that the instruments at this substation remain in speaking condition, the contacts 38 - - 86 being as shown in Fig. 15. 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 contacts 38 - - 86 as shown in Fig. 17, so that at this substation also the instruments are in speaking condition and a local circuit is closed through contacts 85, 86 for the call bell 81. When the subscriber answers the call, a contact 151 which is passingly closed by the switch-hook, energizes magnet 47, which trips the pin 38<1> off the tooth 38<a> into a groove 54. so as to open the ringing-circuit. Restoration of party-line selectors after conversation. This is effected by depressing a key n<111> which causes a complete cycle of impulses to be transmitted to line to step forward the substation selectors. The key n<111> also (by means of a contact not shown in Fig. 1) connects a battery to line to energize a polarized relay r<2> at each substation, which energizes a magnet 205, Fig. 7, which moves an arm 207 into the path of zero stops 208 on the selector disc 36. During this movement the pin 38<1> at both stations travels in the groove 54, the magnet 47 being energized over contacts 74, 77 at the moment when the pin. passes the slot 60, Fig. 8, to prevent the pin from shifting into the groove 58. Operations when a subscriber fails to hang up his receiver. If the receiver has been left off the hook at either substation, the contact 77 is open and the magnet 47 is therefore not energized at the moment when the pin 38<1> passes the slot 60, so that the pin is transferred to the groove 58 and eventually comes to rest on the normal tooth 60<a>. When the receiver is hung up or the switch-hook flicked, the magnet 47 is energized over contact 151, as before described, and trips the pin 38<1> into the groove 54 to stop the ringing. The fact that the receiver is off the hook at a particular substation does not prevent that substation from being selecte