Patent GB-1186940-A (GB)
Title: Improvements in Battery Economy Apparatus
Inventor: WARD MICHAEL HENRY EVANS
IPC: H03F1/02
Filed: 1967-11-30
Abstract: 1,186,940. Transistor circuits; radio signalling. PYE Ltd. 21 Nov., 1968 [30 Nov., 1967], No. 54686/67. Headings H3T and H4L. An arrangement for obtaining reduced power consumption from the battery supply to a radio receiver in the absence of an incoming signal includes a semi-conductor switch device for rendering the direct-current path to the receiver alternately conductive and non-conductive, the switch device being maintained in the ON position upon receipt of an incoming signal to which the receiver is adapted to respond. According to the invention, the switching of the switch device is controlled by a multivibrator circuit of which the repetition rate may be altered but in which the mark/space ratio remains substantially constant irrespective of the repetition rate. A power supply connected to terminals 7, 8, Fig. 1, feeds directly audio amplifier AA, tone detector TD, normally non-conductive bi-stable toggle BT and supply economiser circuits which include economiser/stabilizer ES, the controlling multivibrator MV and locking device L. Economiser/ stabilizer ES, in stand-by condition, supplies via line 9 a succession of narrow energizing pulses at a relatively high repetition rate to receiver circuits R comprising those circuits up to and including the discriminator. The energizing pulses are also supplied to detector/amplifier DA and tone amplifier TA, coupled to the output of receiver circuits R. When a carrier is received, detector/amplifier DA produces a D.C. control bias which is applied over line 10 to tone amplifier TA, over line 12 to an electronic switch S and via line 11 to multivibrator MV, whereby the repetition rate of the pulses on line G is greatly reduced, without alteration of the mark/space ratio. These energizing pulses then persist for sufficient time to enable tone-amplifier TA, which includes a frequencyselective filter, to develop a tone output, assuming the correct calling tone is received from receiver circuits R. This tone output is rectified by tone detector TD to produce a D.C. control voltage which is applied over line 13 to trigger bi-stable trigger BT into its conductive position, whereby electronic switch S is energized. The D.C. bias on line 12 is then conveyed over line 15 to energize normally inoperative audio amplifier AA and over line 16 and delay device D to locking device L, whereby the economiser/stabilizer ES is caused to deliver a continuous output on line G. When the message ceases, the arrangement is returned manually to the stand-by condition by closure of reset switch RS which causes bi-stable toggle BT to revert to the non-conductive condition. Control circuits. Detector/amplifier DA comprises transistor TR1, energized from line 9 via resistor R2, which is rendered conductive by noise signals received over capacitor C1 in the absence of a carrier. When so energized the collector potential is low, so that insufficient bias is applied to the gate of field-effect transistor FET, via diode D6 and delay capacitor C7, to render it conductive. The drain-source path of transistor FET shunts capacitor C5 which in series with capacitor C4 forms the feedback path of multivibrator MV which comprises transistors TR5, TR6. The collector of transistor TR5 is direct-coupled to the base of transistor TR6, while its base is biased via a potentiometer comprising resistors R8, R9, equal in value to resistors R10, R11 respectively, and diode D2 which is of the same material as transistor TR5. The collector circuit of transistor TR6 comprises diodes D3, D4, multivibrator MV forming with economiser/stabilizer circuit ES comprising transistors TR7, TR8, a supply economising arrangement of the type described in Specification 1,185,909. When a carrier is received the reduction in noise causes transistor TR1 to become non-conductive and its collector potential to rise, whereby field-effect transistor FET is rendered conductive: capacitor C5 is then short-circuited and the time-constant of multivibrator MV is then determined by capacitor C4 alone. The collector potential of detector/amplifier transistor TR1 is also applied via terminal 3 to the tone amplifier (not shown) and via resistor R16 to the base of transistor TR2, which forms with transistor TR3 the electronic switch S. Bi-stable toggle BT comprises cross-coupled transistors TR9, TR10 of opposite conductivity type and is normally non-conductive: a lowering of the potential of terminal 5, which is connected to the tone detector (not shown) causes the arrangement to trigger over to the conductive state, whereby transitors TR2, TR3 are energized. The positive potential at the collector of transistor TR1 then produces a positive potential at the collector of transistor TR3, which is applied over a delay network comprising diode D1 and capacitor C3 to bias transistor TR4 conductive. The base of transistor TR5 is then clamped to a low potential, whereby multivibrator operation is inhibited and transistor TR8 rendered continuously conductive to supply a steady current to the line 9. Momentary closure of reset switch RS, in the absence of calling tone, causes bi-stable trigger BT to revert to the non- conductive state, whereby the arrangement takes up the stand-by condition. By holding reset switch R5 closed, the arrangement may alternatively be kept continuously operative to receive signals unaccompanied by the correct calling tone. The arrangement may alternatively use the supply-economiser circuit described in Specification 1,111,006.