Patent GB-760802-A (GB)
Title: Improvements in or relating to impulse receivers for telemetering systems
Inventor: SMITH STANLEY COLIN
IPC: H04M15/10
Filed: 1953-05-06
Abstract: 760,802. Voltage and current measuring. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Feb. 22, 1954 [May 6, 1953], No. 12552/53. Class 37. [Also in Group XL (c)] In a circuit for converting a variable rate of transmission of electrical impulses into a corresponding visual indication, a first capacitance is charged to a predetermined voltage on reception for impulse and is connected for a predetermined period on termination of the impulse, to a second capacitance which is allowed to discharge slowly over the interval between impulses and which is connected to a visual indicator displaying its state of charge on the reception of an impulse; the circuit of the indicator being such that if the voltage of the second capacitance falls below that corresponding to the current reading of the indicator by a predetermined amount due to non-reception of a further impulse, the said reading is rapidly reduced. The receiver of an impulse frequency telemetering system for electrical quantities operates in response to an incoming signal train over line or radio link from a transmitter of the kind described in Specification 760,909, representing e.g. the rectified output of a current transformer in an A alternator circuit, to impulse relay - (Fig. 1) 3 which when operated closes contacts a<SP>1</SP> to B energize relay - shunted by resistance R<SP>8</SP> and 1 closes contacts b<SP>1</SP>, changes over contacts a<SP>2</SP> to charge capacitance C<SP>5</SP> from the H.T. source over resistance R', and changes over contacts a<SP>3</SP> to connect measuring capacitance C<SP>6</SP> (large compared with C<SP>5</SP>) to the grid of triode VT<SP>2</SP>, in shunt with the capacitance C'. On termination A B of an impulse, relay - releases but relay - re- 3 1 mains operated for a short interval due to the shunt resistance R<SP>8</SP> so that capacitor C<SP>5</SP> applies a charge to capacitor C<SP>6</SP> over resistance R 7  after which contacts b<SP>1</SP> open to break the charging circuit. During the interval before the rest input pulse, capacitance C<SP>6</SP> discharges linearly over resistance R<SP>9</SP> and non-linear silicon carbide resistance element NLR, and is recharged from C<SP>5</SP> so that on arrival of successive input im. pulses capacitance C' is charged proportionally to the train frequency which is measured by meter M in the anode circuit of triode VT<SP>2</SP> calibrated in terms of the quantity to be telemetered. On cessation of impulsing, C<SP>7</SP> is rapidly discharged over diode VT<SP>3</SP>, NLR and R<SP>9</SP> to prevent false indications. In a modified receiver (Fig. 2, not shown), at the beginning of each input pulse the measuring capacitance receives the charge of a condenser which has charged during the preceding interval, and at the end of each pulse receives the charge of a capacitance which has charged for the duration of the pulse, and is discharged over a triode anode circuit biased to lower impedance from the anode current of the measuring triode when the pulse rate is high and vice versa. A resistance-capacitance time constant circuit is included in the grid circuit of the measuring tube to smooth out irregularities of the indications.