| 摘要 |
1,140,456. Automatic speed control. XEROX CORP. Sept.27, 1966 [Oct. 1, 1965], No. 43086/66. Heading G3R. [Also in Division H2] In a synchronizing system, oscillator 10 is connected to frequency divider 12 whose output is amplified and applied to motor 16 having a permanent magnet rotor so as to afford a fixed relationship between the position of the motor shaft and the phase of the applied voltage. The motor is geared to facsimile drum 20 to which is fixed a cam 26 for operating periodic contacts 27, 29, associated with low-voltage source 30. A circuit 34 separates a synchronous signal from incoming information signals applied to terminal 32, a differentiating capacitor 40 ensuring that AND gates 36, 38, respond only to the leading edge of the received synchronizing signal. The other input of gates 36, 38, are connected to contacts 29, 27, respectively. The reset input of flip-flop 42 receives a signal from gate 38 to indicate an out-of-synchronization condition, whereby amplifier 44 energizes lamp 46. When frequency divider 12 corresponds to a count of 60, gate 50 generates a signal which passes through gate 48, due to the simultaneous presence of the signal from flip-flop 42. The signal from gate 48 passes through OR gate 52 and capacitor 54 and is applied to the re-set terminals of stages 1, 2, 3, of divider 12 which now delivers a higher frequency signal to the motor. The drum catches up with the incoming synchronizing signals so that coincidence is detected by gate 36 between these signals and those from the contact 29. Flipflop 42 changes-over to extinguish lamp 46, pulses from gate 50 being prevented from passing through gate 48 thereby restoring the unit 12 to its normal dividing ratio. Pulses from the flip-flop 42 now coincide with the incoming synchronizing signals which are passed through gates 56, 52, to re-set the divider 12 to zero whereby the phase of the voltage applied to the motor is regulated within narrow limits. The system may be modified to operate as a combined transmitter and receiver, the units corresponding to the gates 48, 56, being disabled in the transmitter mode so that the divider 12 functions as an ordinary divider and motor 16 operates at a steady speed. A three-input AND gate detects coincidence between the outputs of stages 5 and 6 of the divider and the closure of contact 29, the output of the gate being a pulse occurring once per revolution of drum 20 and accurately timed with respect to the position of the drum. This pulse serves as a transmitter synchronizing signal and is combined with information signals in an OR gate, Fig. 2 (not shown). |
