Patent GB-335240-A (GB)
Title: Improvements in or relating to electric signalling and control systems
IPC: G08C15/00
Filed: 1929-06-18
Abstract: 335,240. Lipman, S. June 18, 1929. Tell-talc apparatus; selective remote control systems.-A constant voltage generator, preferably of the flat disc type is used as the voltage source in potentiometer systems of indicating or testing. The constant voltage is ensured by driving the generator at a constant speed, by means such as a clockwork mechanism, synchronous motor or a constant speed centrifugal friction-clutch type motor and the potentiometer may consist of either a variable resistance or a condenser and inductance one of which is variable. The embodiments described include the use of the generator as the voltage supply for (1) tell-tale appartus, (2) indicating the product of two variable quantities (volt-amperes), (3) summation of differences of indications (4) direct and alternating current type potentiometers, (5) indication of position of switches and (6) remote selective control. In tell tale apparatus, such as indicating at a remote point the level of a liquid, the potentiometer tapping is varied by an attachment to the float and an ammeter type instrument at the receiving end responds to the current variations. If used with graphic type recorders the constant voltage generator can be driven from the driving mechanism of the recording chart. A system of this type is indicated in Fig. 4 in which two recording apparatuses are shown. The charts are driven at a definite rate by either clockwork or a synchronous motor D. Geared to the driving mechanism is a shaft C1 carrying three constant voltage generators A1, A2, A3. The output from two of the generators is connected to potentiometers J1 J2 which are tapped by arms L1, L2 controlled by the instruments K1, K2. The meter M records the sum or difference of the two outputs depending on whether the outputs from J1, J2 are additive or in opposition. Alternatively M may be replaced by an integrating ampere-hour or watt-hour meter registering total current or power in the two circuits or may be replaced by a relay energizing when a predetermined fixed value is exceeded. The shaft K3 which rotates once in 24 hours may carry an arm L3 moving over a potentiometer J3, Meters M3-M6 fitted at remote points, which may be ordinary spring controlled milliammeters, will indicate the correct time so long as the shaft K3 is in operation, the meters being reset to zero every time the arm L3 crosses the gap in the potentiometer. Fig. 6 shows a system of indicating on meters M, M1, M2 the reading of a spring controlled ammeter or voltmeter K. The constant voltage generator A, B is driven through centrifugal friction clutch mechanism. The shaft c of the instrument K carries an electric motor a, b which moves the pointer m of K back to a zero position o and when this is achieved the current flowing through the moters M, M1, M2 is proportional to the quantity measured by the instrument K and the apparatus can be calibrated accordingly. The selection of apparatus at a remote point is indicated in Fig. 8. A pointer L is moved to a position representing the apparatus 6-10 it is desired to select, altering the current flow over the circuit N and upsetting the balance of the relay m at the remote station. The pointer o deflects and completes a circuit for reversible motor a which drives shaft C4 carrying arm l. Arm divides the resistance i', j<2> and movement continues until the current in the coil M3 is sufficient to re-balance the polarized relay m. The shaft C4 also carries contact arms X, X1 which are set by the movement of the shaft to connect the line circuit X7, X6 with the apparatus required. Systems are also described in which two instruments such as voltmeter and an ammeter may control (1) a single watt-meter or watt-hour meter giving a result proportional to the apparent power or volt-amperes, or (2) a single ohm-meter giving a reading proportional volts to the ratios of the two quantities, amperes i.e. impedance, resistance or reactance. A constant voltage generator may also be used as the voltage source on direct current potentiometers of the Crompton or Drysdale type or for alternating current potentiometers such as the Gall or Campbell Larson.