GB997744A - Improvements in or relating to alarm systems - Google Patents

Abstract

997,744. Alarm apparatus. L. P. V. PACK, and E. E. ELLIOTT. April 20, 1964 [April 23, 1963; Oct. 25, 1963], Nos. 16060/63 and 42268/63. Heading H4K. An alarm apparatus, e.g. for a burglar alarm, comprises detector switches which, when closed, cause the apparatus to be connected to a telephone line and a playback apparatus to be energized to reproduce signals from two recordings one of which produces a signal to control the transmission of, first, dialling impulses, and then, a message, from the second recording. The apparatus may also operate a local alarm if the telephone lines have been cut, or if the telephone line has been engaged by an incoming call. Fig. 1 shows a block diagram of the apparatus in which the apparatus is switched on ready for operation by closing the ganged switches 17 and 18. On the alarm event occurring, e.g. a fire or burglary, one or more of switches 22 closes and relay 19 operates to self hold on contact 19a, to connect the drive to tape motor 11 over contact 19b, and to connect the apparatus to the telephone lines A and C over contacts 19c and 19d. The tape drive motor 11 drives a pre-recorded tape past upper and lower track heads 12 and 13, the lower track having a constant tone recorded on it which is detected by amplifier 23 to operate relay 24 which completes the circuit across the telephone line at 24b and connects the upper track amplifier 25 to a dialling impulse relay 26. After a delay sufficient to allow dialling tone to be received dialling impulses are reproduced from the tape and via amplifier 25 operates relay 26 to cause the dialling impulses to be sent over the telephone line. On completion of dailling the tone on the lower track ceases and thus causes relay 24 to be released which removes the short circuit from the line at 24b, opens the bell circuit at 24c and connects the upper track amplifier to the telephone line via amplifier 27 to relay the message on the upper track to the line. After the conclusion of the message a foil strip on the tape bridges contacts 37 to operate relay 36 so breaking the circuit for relays 19 and 11 to disconnect the apparatus from the line and to de-energize the tape transport motor. An additional contact on relay 36 may operate a local alarm bell. A line ringing signal detector 48 and a line continuity detector 49, both shown in detail in Fig. 2, are provided. Circuit 48 rectifies a ringing signal on the line and operates a relay 53 which opens contacts 53a in the tape drive motor circuit and thus delays operation of the device until the ringing signal stops, when the procedure detailed above will come into operation. Should the outgoing lines be cut, when relay 19 operates initially to connect the apparatus to the line no D.C. signal will appear on the lines 46 and 47 and relay 57, which is normally operated by the D.C. signal from the line, will remain unoperated. Contact 57d will therefore remain closed and when relay 24 closes, due to the reception of the tone signal on the lower tape track, relay 36 will be energized to disconnect the apparatus and to operate the local alarm bell. Normally the D.C. signal on the line causes relay 57 to operate thus disabling contacts 24e in the operating circuit of relay 36. If required the ringing detector relay 53 may have additional contacts in parallel with contacts 37 which close when a ringing signal is detected and thus operate the relay 36 and the alarm bell immediately.