Patent GB-190609583-A (GB)
Title: Improvements in Party-line Telephone Systems
Inventor: MCKINSEY NOBLE SAMUEL
Filed: 1906-04-24
Granted: 1907-01-17
Abstract: 9583. McKinsey, N. S. April 24. Telephone systems ; telephones.-Relates to a step-by-step party-line telephone system in which one line-wire of each party line is grounded at the exchange through a resistance greater than that of any other talking- circuit in the system. The exchange is called by earthing the other linewire through a resistance, and when the desired connexion has been made the connexion remains under the control of the calling subscriber, who by cutting out the resistance can increase the current flowing and thus actuate a clearing-out signal at the exchange, as well as restore the selecting - mechanism to its normal position at all the stations on the called subscriber's line. To this end, the operating-magnet of the selecting-mechanism has two armatures, the one actuated by small currents to move the selector, and the other attracted by larger currents to return the apparatus to zero. Fig. 13 shows the connexions of the subscriber's apparatus. The receivers 6 at all stations are normally shunted by a circuit including the wire 100, contact 97 of the bell, contact-spring 182, and the wire 118. The bell is in multiple with the microphone, so that, on removal of the receiver, current flows from the battery 81 through the primary 85 and microphone 87, and through the wire 92, bell coils 95, and the wire 100 to the common point 55, and thence through contacts 45, 46, wire 59, clock-work mechanism, and " line - controller " 12, contact 22 (contacts 21, 22 engaging the part 10 of the " line "controller" when the hook lever is raised), and wires 91, 143 back to the battery. The bell armature is thus permanently attracted, breaking the shunt round the receiver at the point 97. Fig. 3 shows the system as a whole. To call the exchange, a subscriber removes his receiver, thus closing a circuit from ground 32 through the resistance 27, contact 21, line-controller 12, clock-work frame 13, line-wire 2, indicator drop 36, and the resistance 5 to the grounded battery 4. The resistance 5 is greater than that of any other talking-circuit in the system. The operator inserts the plug 37 into the jack 68, completing a talking-circuit from the receiver 6 via point 55, contact 45, hook lever, wire 59, clock-work frame 13, wire 33, line-wire 2, contact 60, contacts of operator's listening-key 41 and talking-circuit 40. condenser 65, contacts 67, 68, 69, 70, line-wire 1, contacts 43, 44, and the secondary 75 back to the receiver. If the wanted subscriber is on a different line, the operator inserts the plug 37<1> in the jack of that line and sends a number of impulses corresponding to the number of the called subscriber by depressing the key 103 to actuate the selector magnets 108<1> of the stations on this line. This circuit passes from ground 32 at the calling-station through resistance 27, contacts 21, 10 to the line-wire 2 as before, contacts 60, 61, 104, 102, wire 105, key 103, contacts 102<1>, 104<1>, 61<1>, 60', and the line-wire 2<1>, the circuit then dividing and passing at each station through the wire 107<1>, magnet 108<1>, line-wire 1<1>, contact 69<1>, and the resistance 5<1> to the earthed battery 4<1>. The magnets 108<1> control an escapement device which moves round the arm 137<1> at all the stations, so that at the selected station it engages a contact 140<1>, thus completing a local bell circuit from the battery 81<1> through the contact 140<1>, arm 137<1>, clock-work frame 13<1>, wire 59<1>, hook 46, contact 47<1>, and the bell, and back to the battery. The bell thus rings until the called subscriber breaks contact at 47 by removing his receiver. The called subscriber's talking-circuit is precisely similar to that of the calling subscriber, the two parts being united by the condenser 65 in the cord circuit. The called subscriber cannot give the clearing-out signal, because the rotation of the clock-work has allowed the line-controller 12 to move in such a manner that it no longer engages the contacts 21, 22 when the hook lever is raised. If the called subscriber hangs up his receiver before the calling subscriber has given the clearing-out signal, the contact 47 is closed and his bell again rings. When the calling subscriber hangs up his receiver, he short-circuits the resistance 27, thus increasing the current flowing through the circuit of the magnets 108' previously described. This increased current operates the clearing - out signal 150 at the exchange, and also restores the selecting - mechanism at all stations on the line of the called subscriber by causing the magnets 108<1> to attract their second armatures (referred to in greater detail in the description of Fig. 2). If the wanted subscriber is on the calling subscriber's line, the operator removes plug 37 and inserts the plug 111 in the jack 39, the tip 112 breaking contact between the parts 69, 70, and the shank 113 engaging the ring 68. Fig. 15 shows the construction of the jack, in which the contacts 69, 70 are separated by the plug 111 but not by the shorter plug 37. By this means, the line-wire 2 is graduated at 32 at the calling subscriber's station and the line-wire 1 earthed through the tip 112, ringing-key 103, shank 113, collar 68, and the battery 4. The magnets 108, being bridged across the line-wires 1, 2, can thus be operated as before by the ringing-key 103. Fig. 2 shows the magnet 108 with its two armatures 121, 122, the latter being farther from the magnet, so as to be only attracted by strong currents. The armature 121 is attached to levers 123, secured to the rocking shaft 124, the levers being connected at their other ends to a pin 125, passing through a slot 126 in the end of a lever 127, the other end of which is attached to the armature 122. The end of the lever 127 is shaped as shown in Figs. 2 and 9, to form an escapement for pins 134 on the wheel 129 of a clock-work train. Each attraction of the armature 121 allows the wheel 129 to rotate half a revolution, the selecting- arm 137 being moved round one step. The local bell circuit is completed when the arm 137 engages a spring-mounted arm 138. When the armature 122 is attracted by a stronger current, the lever 127 is raised and allows the wheel 129 to rotate freely until an arm on the wheel 131 engages a stop on a lever connected with the armature 122. When the circuit is again broken, this stop releases the arm, and the wheel 129 rotates till one of the pins 134 engages the lever 127. Fig. 2 also shows the construction of the hook-switch contacts. Three of the seven springs 43 ... 49 are longer than the others and have their ends inserted in notches in the block 50, which is pivoted at 52 in such a way that when the hook lever 7 is depressed, the springs 44, 46, 48 engage with the springs 45, 47,49 respec. tively. Fig. 14 shows the arrangement of the magnets 108 of several stations on the two line-wires, from which it will be seen that, when one subscriber calls by completing the connexion 170, all the magnets 108 are energized in multiple, and this is utilized to prevent any other subscriber from obtaining access to the line-wires by means of the arrangements shown in Fig. 9. On the back of the gear-wheel 131 in the clock-work train is provided a crown-wheel 155, having therein a gap 156, through which a pin 157 on the line-controller can fall. When a subscriber calls, the magnets 108 of all the other subscribers on the same line are energized and the wheel 131 rotates sufficiently to allow the pin 157 to fall through the gap 156, thereby bringing the end 10 of the line-controller out of reach of the pin 9 on the hook lever 7, and thus preventing the pin from pressing the line-controller against the contacts 21, 22 to effect a call as previously described. The extension 160 of the line-controller moves a 'busy' signal 162 into display position when the pin 157 falls through the gap 156. At the calling-station, the pin 157 is raised out of the gap 156 when the line-controller is lifted by the act of calling-, and lies on the top of the crown-wheel. When the calling subscriber hangs up his receiver, the line-controller is thus held against the contact 22 until the pin 157 again falls into the gap 156, thereby prolonging the clearing-out current sufficiently to keep the armature 122 attracted until the clock-work mechanism has returned to its normal position.