Patent GB-1226556-A (GB)
IPC: H04M11/04
Filed: 1968-02-20
Abstract: 1,226,556. Automatic exchange systems. GLIDDEN ELECTRIC CORP. 20 Feb., 1968, No. 1351/68. Heading H4K. A telephone substation has an automatic alarm system and data reading device, appropriate code messages being sent over a connection automatically set up, the alarm system functioning to override operation of the normal telephone set which in its turn overrides the data reading device. The alarm condition is derived specifically from a fire alarm circuit involving a chain of heat sensitive switches and functions to call a fire station. The data reading device is a meter which signals a power utility each time a fixed quantity has been consumed. a clockwork sequence switch referred to as a data dialler 28 and comprising a drum or disc with sixteen wiper contacts is employed to govern automatic dialling of a preset number in its first quarter revolution and, after a quarter revolution to allow time for response by the called station, governs transmission of a preset message in the form of coded tones in the last half of its cycle. The sequence switch recycles continuously until the substation detects a tone by means of tuned transistor amplifier 44 such tone being reverted from the receiving station to indicate that the message has been recorded. The arrangement is preset to send either loop disconnect impulses or multifrequency tones, the latter being produced by selectively connecting appropriate capacitors in the circuits of transistor oscillators 34, 36. The coded tones constituting the message are produced by control of the oscillators 34, 36, from the sequence switch 28, the tones comprising a continuous tone from one oscillator and an interrupted tone from the other oscillator. At the receiving station the continuous tone operates a timed transistor amplifier 52 and the interrupted tone is repeated by a transistorized multivibrator 60 to operate a code recorder 64, which may be a tape recorder, and an alarm 66. Receipt of a message also operates a time and data recorder 54 which is also employed to record the times at which the exchange fails to provide a requisite voltage on the line and when such voltage is restored. The oscillator 62 reverts the tone to indicate to the calling station that the message is being recorded and the need to recycle no longer exists. Whenever the fire alarm circuit initiates sending of an emergency call it also triggers off a compressed air operated horn shown as alarm 32. The horn operates regardless of whether the exchange line is or is not serviceable and is such that it must be reset manually. The emergency call condition also switches on a transistor blocking oscillator to light a neon lamp in the operational indicator 50, the voltage applied to the oscillator being such as to cause the neon to glow continuously. If the exchange line becomes unserviceable, as indicated by departure from normal voltage levels, a so-called line failure logic circuit 48 switches on the blocking oscillator in the indicator 50 using a lower voltage so that the neon flashes. The blocking oscillator is powered from a battery normally charged over the exchange line.