Patent GB-399675-A (GB)
Title: Improvements in alarm devices for use in connection with automatic telephone systems
IPC: H04M1/274
Filed: 1932-12-08
Abstract: 399,675. Automatic exchange systems; gramophone pick-ups. TUSCHER, J. E., 15, Rue Mozart, Petit Ivry, and SPIRO, M., 25, Rue de Ponthieu, Paris, both in France. Dec. 8, 1932, Nos. 34825 and 34826. Convention dates, Dec. 9, 1931, and Sept. 28, 1932. [Class 40 (iv).] Relates to sub-station apparatus which, in order to give an alarm, e.g. in case of burglary, automatically calls up the alarm receiving station and transmits thereto a message from a gramophone record. The impulse transmitter comprises a series of impulse discs, one for each digit, mounted coaxially on a drum and spaced apart, the drum being given a rotational and axial movement so that the discs engage the impulse springs in turn. The use of a single disc for a single digit call is mentioned. In one arrangement, Figs. 1 to 3 (not shown), the impulse transmitter and gramophone are driven by an electric motor but in the arrangements described below, spring motors are used, and in one modification successive calls may be sent to the same or different stations. When the protective circuit is closed, relay 14, Fig. 4, releases flap 17 which drops on and releases a pivoted catch 18 normally engaging a stop 20 on the gramophone turntable 19. The release of the turntable permits spring drum 1 to drive the impulse transmitter n and a ratchet wheel 48 for a purpose described later, while the governor controlled contacts b, c, d, Fig. 6, disconnect the normal telephone set 121 and connect the emergency set comprising pick-up m and impulse transmitter n, in parallel across the line k. During impulse transmission the pick-up m is short-circuited over springs e, f and the impulse springs f, g are shunted by condenser w and resistance r to prevent sparking. The impulse transmitter, Figs. 9 and 10, comprises a spindle 25 driven by gears 6, 9 and having a cross-pin 28 normally in driving engagement with a slot in drum 30 which carries a number of impulse wheels 24 (one for each train) separated by washers 29. The bore of the drum is threaded to run on a fixed screw 26 through which the spindle 25 passes freely so that the drum, on rotation, moves downwardly and the impulse wheels operate, in succession, the impulse springs f, g. Each impulse wheel has at least half its periphery plain so as to give the interdigital pause. When the drum has moved down past the impulse springs, the driving pin 28 is disengaged from the drum and the springs e, f separate to remove the shortcircuit across the pick-up, the circuit of which includes an adjustable series resistance r<1> for adapting the apparatus to lines of varying resistance. The message is recorded on a width of record (say for 40 turns) corresponding to one revolution of the spring drum and when the pick-up has passed over the record, a finger 41, Fig. 4, adjustably mounted on the tone arm 33 engages an upstanding pin 43 on the drum, the end of the pin being so shaped that it lifts the arm and returns it to the starting position to repeat the message. The drum 1 carries peripheral pins 46, Fig. 8, engaging ratchet wheel 47, which drives a screwed spindle 48 until its head 50 engages a fixed abutment whereby the drive is stopped after a suitable time period, and the restoration of the governor controlled contacts releases the connection and reconnects the ordinary telephone set. Modification for sending successive calls to the same or different stations, Fig. 4 (not shown). The spindle 48, Fig. 8, of the ratchetdriven device which ultimately stops the spring drive is extended downwards and carries two sets of cams. The first set controls contacts in the pick-up circuit to open the circuit between the calls and therefore release the connections, while the second set controls a clutch which connects up the drive for the impulse transmitter at the commencement of each call. The transmitter carries as many sets of impulse discs as are required for setting up the successive calls, all of which are sent out in response to a single operation of the protective circuit. Construction of pick-up. The carbon diaphragm 37 of a microphone m is vibrated by an adjustable screw 38 mounted in the stylus arm 35 and passing through a resilient lining 40 secured inside the casing 31 to damp stray vibrations.