GB752910A - Improvements in or relating to radio receivers provided with time switch control devices - Google Patents

Abstract

752,910. Radio receiving apparatus TELEFUNKEN GES. FUR DRAHTLOSE TELEGRAPHIE. March 2, 1954 [March 2, 1953], No. 6041/54. Class 40 (5). In a radio receiver comprising a loud-speaker, there is provided a time-switch which is adapted to switch the receiver on at a predetermined time and is adapted to direct, after a predetermined interval, alarm signals to the loudspeaker, over-riding manual control means being also provided which is adapted to prevent the transmission of the alarm signals to the loudspeaker. A shaft rotating continuously at the rate of once every 12 hours carries discs 1 and 2 each having a notch therein. At a predetermined time, determined by the position of disc 1, the switch 4 closes thus switching the receiver on. After a further predetermined interval, which may be adjustable, the switch S operates due to the spring-urged plunger St entering into the notch 3 in disc 2. In the arrangement shown the grid of the output valve R feeding the loud-speaker (not shown) is normally connected via the switch S to the volume control resistor P; when however the switch S operates the full signal voltage, providing an alarm signal, is applied to the valve R. The switch S may be prevented from operating or restored to its original position after operation by depressing a push button 5. The button is held in its depressed position until released by further means (not shown) which may comprise means operated by the disc 1 after the notch 3 has passed the position in which the plunger St can engage therewith. In a first modification, Fig. 2 (not shown), operation of switch S causes a mainsvoltage signal to be applied to the grid of the output valve. Fig. 3 (not shown) shows a twovalve output stage having negative feedback to the first valve. Operation of the switch S causes the feedback voltage to be applied to the second valve, so that the feedback now becomes positive and causes the second valve to oscillate and thus apply an alarm signal to the loudspeaker. The switch S may alternatively be arranged to reverse the sign of the feedback voltage to the first valve. In a final modification, Fig. 5 (not shown), the switch S controls a vibrator energized from the heater supply voltage, the voltage pulses derived from the vibrator being applied to the grid of the output valve.