| 摘要 |
<p>1391406 Lamp brightness control circuits SPERRY RAND CORP 12 June 1973 [29 June 1972] 27805/73 Heading H2H Variable intensity illumination apparatus comprises a lamp 49, a monostable multivibrator 35 and an astable multivibrator 33 coupled to drive the monostable multivibrator from a stable state into a quasi-stable state in response to a selected edge of the astable multivibrator output pulses. The brightness of the lamp may be increased by moving the adjustable arm of a potentiometer 53 towards the right thereby increasing and decreasing the series resistance of the resistance-capacitance networks of the multivibrators 33 and 35 respectively. This movement reduces both the pulse repetition frequency of the multivibrator 33 and the duration of the output pulses of the multivibrator 35. The trailing edges of the pulses from the multivibrator 33 trigger the multivibrator 35 and the output pulses from the complementary output terminal Q of the multivibrator 35 have an increased duration so that the lamp is bright. Opposite movement of the potentiometer arm reduces the duration of the pulses supplied to the lamp and the lamp is therefore dimmed. The multivibrators are formed as an integrated circuit and the leading edge of the astable multivibrator pulses may be used to trigger the monostable multivibrator.</p> |
