Patent GB-191218262-A (GB)
Title: Improvements in or relating to Fire Alarm Signal Boxes for Automatic Telephone Systems.
Inventor: BOULT ALFRED JULIUS
IPC: H04M11/04
Filed: 1912-08-08
Granted: 1913-08-07
Abstract: 18,262. Boult, A. J., [Denio General Electric Co.]. Aug. 8. Fire-alarm systems and apparatus.-A firealarm signal transmitter, for use on a telephone subscriber's line in an automatic exchange system, sends first the numerical sets of impulses necessary for operating the automatic exchange switches to select a line to the fire station, and then the code signal characterizing the particular transmitter, but if the line is already in use by the telephone subscriber the sending of the impulses is delayed automatically until the line has been cleared by the release of the exchange switches. The numerical impules are dispatched by a disk 19 controlling a spring i; the code signal is sent by a disk 20 controlling a spring g, and the necessary changes of the connexions at the different stages of the operations are effected by a pair of cam-disks, one of which controls the springs a, c while the other controls the spring e, as shown in Fig. 6. The cam-disks are on the same shaft as a toothed wheel 24, Fig. 1, and are rotated through an angle corresponding to the space between two teeth, or one-sixteenth of a turn, twice in each revolution of the disks 19, 20, the shaft 3 being provided with arms 22, 22<a>, which first lift a detent 23 from the wheel 24 and then turn the wheel forwards so that the detent drops on to the next tooth. The operations are as follows. The depression of the alarm push 12, by removing a stop from a spring - tensioned slider 7, Fig. 3, sets free a fan 6 on the axle of an escapement 5 and permits a spring 2 to drive the shaft 3. As the cam-disks move from normal to their first position, the springs a, c are shifted to the left to disconnect the two sides of the line V, R from the subscriber's instrument A. When the first projection on the disk 19 comes into action, closing the springs i, l, k, a polarized magnet X, Y is connected between the lines V, R. If the subscriber A is in conversation with some other subscriber, there will be current flowing in the line V, R, but in this case the polarized magnet X, Y is energized only if the subscriber A is the called subscriber, the incoming and outgoing connexions of the lines at the exchange being reversed so that the polarity of the current in a talking subscriber's line depends on whether he originated or received the call. If the magnet X, Y is energized, it moves an arm 15, Fig. 3, to lock the escapement 5, 6, so that the further operation of the transmitting-device is prevented until the magnet is de-energized by the release of the automatic switches, which takes place in the usual way when the calling subscriber, finding himself cut off from the subscriber A, hangs up his instrument. If the subscriber A had been the originator of the previous call, the transmitter would continue its action without interruption, the automatic connexion being released by the grounding of the line through the springs e, f, i, k as the cam-disks pass through the first position. In the second position of the cam-disks, the ground connexion is removed by the opening of the springs e, f, and in the third position the springs h, c, are opened to clear the line. In the fourth position, the contact e, f is closed, connecting ground to the spring i, and the disk 19 moves the spring i against the springs j, k to send over the vertical and rotary lines V, R, the impulses necessary for operating the exchange switches to connect the line V, R to a fire-station line. The exchange system described is one in which line-switches, first selectors, and connectors of the well-known threewire Strowger type are employed, and the firestation lines are wired to terminals in the first selectors. In the fifth position, the spring e is moved to the left, so as to be capable of engagement by the spring g under control of the signal disk 20, and code impulses are sent over the line V and through the exchange to a relay and recorder at the fire station. In the sixth position, the contacts h, c and e, f are closed, so that the next closure of the springs i, k, l connects ground to the wires V, R to initiate the release of the exchange connexion. In the seventh position, the wires V, R are disconnected, to complete the release operations, and in the eighth or normal position the connection of the subscriber A to his line V, R is restored by the closure of the contacts a, band c, d.