Patent GB-831151-A (GB)
Title: Improvements in or relating to information-conveying system
Inventor: DICKINSON HORACE
IPC: G08C15/00
Filed: 1956-08-07
Abstract: 831,151. Electric selective signalling systems. VAPOR RECOVERY SYSTEMS CO. Aug. 7, 1956, No. 24190/56. Class 40 (1). An information conveying system for conveying to a distance the position of a movable sensing element uses the reflected binary code. Transmitter.-As described for indicating at a remote point the height of liquid in a tank, the liquid height is converted through a float 22, Fig. 2C, metal strip 25 and gearing 27, 28, 29 into a corresponding angular position of an " inches " code disc 30 and a " feet " code disc 32. Each disc has a coding surface, Figs. 7, 8 (not shown), sensed by the sensing heads 49A-55A and 67A-63A respectively, whereby angular position is translated into a corresponding " reflected binary number. A twenty-four position scanning commutator disc 34, Figs. 2C, 10, has two rings of contacts engaged respectively by two brushes 37- 38 on a rotatable arm 36, the brush 37 engaging the twentyfour outer relatively angularly wide series of contacts 40, 41 ... 63 (for forming long pulses). While the brush 38 sequentially contacts the twenty-four relatively narrow inner contacts 70, 71 ... 93 (for short pulses) which are connected to the conducting ring 95. A third innermost brush 39 continuously engages an innermost ring 97. The commutator scans the upper six contacts of a plate 130, the " inches " and " feet " sensing heads sequentially to produce a train of twenty-four short or long pulses (dots or dashes) dependent on the angular position of the code discs 30, 32 and including a number associated with the particular tank being gauged for which purpose markings are applied to the upper six terminals of the plate 130. These pulses appear on the line 11, Fig. 2C. Receiver.-Closure of the start switch 224, Fig. 2D, at the initiation of a gauging cycle operates a relay 226 and applies power over the line 13 to energize the transmitter relay 102 and apply A.C. to the motor 102 which causes the commutator arm 36 to rotate for one revolution before the current is cut off by the cam switch 110. The resulting pulse train over line 11 correspondingly pulses the line relay 124. Closure by relay 124 of the contact 124A applies a positive voltage from the lead 212 to the stepping switch drive magnet 222 which immediately after the first pulse steps the switch arm 222A from its home position to the contact B whereupon the off-normal contacts 222B, 222C close and relay 220 is energized. Each subsequent line pulse then energizes the stepping magnet 222 and de-energizes the relay 220. Due to the condenser 240 only a long pulse gives time for the normally open contact 220A to close thereby applying a positive voltage through the contacts 222B, 220A to the switch arm 222A. Then, as the switch arm 222A is stepped by the line pulses, only long pulses mark the arm 222A whereby magnets in the decoder, Fig. 2A and Fig. 2B (not shown), are energized and lock in accordance with the transmitted code signal overlines B-H, K-R, T-Z. At the end of the gauging cycle the switch arm 222D has been stepped to contact 25A to apply positive potential over a lead L to the decoder so that lamps indicative of the liquid level and tank number are illuminated. A relay 229 is energized through the contact 124A as the first pulse is received and operates a relay 228. The relay 229 and hence the relay 228 remain energized during the entire pulse transmission by virtue of the condenser 245. Positive voltage from the lead 212 thus remains applied to the line 13 when the start switch 224 is released. On completion of the twenty-four pulses the relay 229 is de-energized and releases the relay 226 to de-energize the line 13 so that the transmitter relay 102 is de-energized to interrupt the motor drive circuit, but the motor 108, continues to run until the cam switch 110 opens and the transmitter is then in position for the next gauging cycle. The receiving apparatus may be reset by operation of the reset switch 225 which interrupts the holding circuits for the decoder (Fig. 2A) and applies positive voltage from the lead 212 to the stepping magnet 222 which then advances by self-interruption to the home position. Code employed.-Liquid level measurements up to 50 feet and involving tens of feet, units of feet, inches and eighths of an inch are translated into a binary code employing three digit positions each for the tens of feet and eighths of an inch and four digit positions each for the units of feet and inches, a measurement (such as 49 feet 11# inches) thus being represented by fourteen binary digits. To each item in the units of feet, inches and eighths of an inch measurements correspond two distinct binary digit groups selected one from each of two series, the series used for each item depending on whether the next higher item is even of odd and the two series for each of the units of feet, inches and eighths of an inch being mirror images each of the other when written out vertically. Thus the coded measurement of fourteen binary digits has the " monophylic " property that only one code element changes for each increment. In a modification (Figs. 2E, 5, not shown) means are described for selecting by a telephone-type dialling system a particular one of a plurality of remote tanks the liquid level of which is then signalled back as already described.