Patent GB-727984-A (GB)
Title: A new or improved electric alarm device
IPC: H04M11/04
Filed: 1952-02-23
Abstract: 727,984. Electric alarm systems. AJZENBERG, L. Feb. 23, 1953 [Feb. 23, 1952], No. 4807/52. Class 118 (1). An alarm device (e.g. for burglary or fire) comprises an automatic dial-type telephone co-operating with means for dialling an appropriate number upon the operation of a detector switch (e.g. due to the opening of a door or a rise in temperature). Manually controlled switches may alternatively be provided. The device may be arranged to dial a particular exchange and number or to dial a code number such as " 999." The device is preferably associated with one or more sound recordings whereby an appropriate message may be transmitted over the telephone system. In the arrangement of Fig. 1, the opening of a switch 11 due to the opening of a door 12, or the closure of temperature -sensitve -switches 13 due to a rise in temperature completes the circuit of a motor 6 and of an electromagnet 19. The electromagnet consequently lifts an armature 4 normally depressing the cradle-switch of a telephone hand-set 1 and allows the dialling tone to commence. The motor 6 simultaneously starts to rotate a partially toothed wheel 10 anti-clockwise. The wheel 10 has seven groups of teeth 10a which engage in succession with a toothed wheel 5 which is secured to the telephone dial and thus cause a predetermined dialling operation to be performed. After the completion of the dialling operation the wheel 10 continues to rotate, allowing a period during which the call may be answered until the circuit of the electromagnet 19 is interrupted by the rotation of a contact ring 9 attached to the wheel 10. Upon the completion of the electromagnet circuit once again, the dialling operation is repeated until the actuated detector switch is reset. In addition, the arrangement comprises motors 17 and 18 actuated respectively upon operation of the switches 11 and 13, and operating sound recordings giving respectively warnings of burglary and fire. Fig. 2 shows an arrangement wherein closure of a detector switch 23 causes the repeated transmission of the number " 999." Closure of the contact 23 causes the electromagnet 19 to raise the armature 4 and starts the motor 6 which drives directly a wheel 26, having teeth over part of its periphery. The toothed portion of the wheel 26 engages with a compound sprocket wheel 27 and is of sufficient length to cause the wheel to rotate three times. The wheel 27 also carries a partially geared sprocket, the geared portion of which engages with the toothed wheel 5 and is of sufficient length to cause the dialling of the number 9. Thus during one complete rotation of the wheel 26, the number " 999 " is dialled, followed by a pause during which the call may be answered. An interrupted contact wheel 9 is also provided to allow the call to be repeated after one complete rotation of the wheel 26. In the arrangement of Fig. 3, the motor 6 drives a partially toothed wheel 36, the toothed portion of which engages sprocket-wheel 5 mounted coaxially with the telephone dial and is of sufficient length to cause the wheel 5 to rotate three times. The wheel 5 drives the dial through a finger 33 which engages a spring 34. The dial rotates until it is arrested by a stop member 35 whereupon the finger 33 passes the spring 34 allowing the dial to return to its normal position, This occurs three times so that the number " 999 " is transmitted. The motor 6 also causes the rotation of a member carrying fingers 37, 38 which actuate an interrupting switch 32 causing the dialling operation to be repeated after every two complete rotations of the wheel 36. Fig. 4 (not shown) illustrates an arrangement for short-circuiting the telephone bell while dialling is in progress.