| 摘要 |
The print wheel and carriage position control signal generators each employ an LED light source for illuminating light sensitive detectors associated with the timing track of an encoder disc rotatably mounted on the print wheel or carriage motor shaft. The detectors are arranged to generate a pair of signal trains having a constant phase displacement in response to rotation of the associated disc. These signal trains are shaped and processed to provide position reference signals used to control an associated position counter unit and an electronic servo control system for driving the associated motor, the servo control system having both a position and a rate mode of operation. A separate light sensor is arranged to be constantly illuminated by the LED source to provide intensity monitoring signals which are compared with a reference voltage in a feedback circuit so that any variation in the light intensity is automatically corrected. The electronic control system provides variable hammer striking intensity tailored to the individual characters or symbols comprising the print wheel font. A memory stores individual address characters each corresponding to different ones of the print wheel symbols and individual hammer intensity characters associated with different ones of the address characters. When the print wheel is rotated to the proper position, the corresponding hammer intensity character is fetched from memory and used to specify the intensity with which the symbol is impressed against the print medium by a solenoid hammer drive unit.
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