GB1427133A - Vehicles including monitoring and/or controlling apparatus - Google Patents

Abstract

1427133 Selective signalling SMITHS INDUSTRIES Ltd 26 Feb 1973 [24 Nov 1971] 54677/71 Heading G4H [Also in Division H3] Apparatus for interrogating sensors 103 in units 105 and for controlling electrical devices 106 in a vehicle comprises a control unit 110 which sends and receives pulse signals of variable amplitude and width circulating in a closed loop 109. The signals take the form of successive cycles of 64 pulses, Fig. 3(a): one large-amplitude start pulse followed by 15 sensor unit (105) pulses and 48 operative unit (108) pulses, each unit 105, 108 being allotted a particular time slot in a cycle. The settings of 48 switches in a console 111 (Fig. 4, not shown) are used to control the on/off states of devices 106, and a display panel 112 (instruments and warning indicators) is provided for the sensor readings. Each sensor unit 105, Fig. 6, comprises means 122 for detecting the start pulse (sync check) and means 123-4 for counting the time slots 0-15 until the corresponding time slot occurs, when it enables a #-# modulator 126-132, Fig. 10 (not shown), and a pulse amplitude modulator 125: the #-# modulator converts the sensor reading into a stream of 1, 0 pulses which are converted into a stream of pulses such as 2 and 3 of Fig. 3. These pulses are transmitted one per cycle in the time slot for that unit (i.e. the reading is sampled once per cycle). Each of the command pulses 16-63 emerging from a modulator 119, Fig. 4 (not shown), in control unit 110 is either of full or half width (e.g. 16, 17, Fig. 3) corresponding to on/off settings of switches 111. Each unit 108, Fig. 7, comprises means 138 to determine the width of the corresponding pulse and to provide an output to a command verifier 139 (Figs. 13, 14, not shown) which checks that a change in width is accompanied by four successive pulses of the new width (one in each of the next four cycles): if so, then a bi-stable circuit 140 outputs a signal which causes a switch 141 to connect/disconnect the device 106 with/from the power supply 102. The signal from 140 also causes a modulator 136 to place a pulse in the corresponding time slot which is of either full or half amplitude to indicate that the device has been turned on or off. Pulse modulation may be effected by connecting or disconnecting a respective resistor into the loop. The sensors may monitor liquid level, temperature, pressure, velocity &c. and the devices may be, e.g. a rear screen heater.