GB872788A - Improved power supply apparatus - Google Patents

Abstract

872,788. Rectifying. DICTAPHONE CORPORATION. Aug. 29, 1958 [Sept. 18, 1957], No. 27830/58. Class 38 (2). [Also in Group XXXIX] The amplifier 38 (Fig. 2) of a dictating machine is supplied with D.C. from mains 18 through rectifier 36, the values of the resistors and capacitors in the network 40 being so chosen that 38 receives the same voltage whether the mains 18 are D.C. or A.C. The relatively heavy intermittent loads taken by the solenoid 34 energized on closure of start-stop switch 12 and the solenoid 50 energized on closure of playback switch 14 are prevented from causing fluctuations in the voltage supplied to amplifier 38 by shunting each of the solenoids by a resistance and capacitor in series 52, 54 and 56, 58, the values of the capacitances being so chosen that connection and disconnection of 34 and/or 50 does not affect the voltage supplied to 38. Solenoid 34 controls a clutch unit 24 which connects the main drive-shaft of the dictating- machine to motor 22. Solenoid 50, when energized, switches the input of amplifier 38 from the microphone to the pick-up head of the machine and the output of the amplifier from the recording head to the microphone which then serves as a loud-speaker. Fig. 4 shows another arrangement in which load 80 may be the amplifier and 96 and 106 the solenoid coils and surge resistors 76, 92, 102 are arranged as shown to reduce the ripple voltage applied to the coils.