Read Panasonic KX-DT390RU Service Manual online
7
KX-DT390RU/KX-DT390RU-B
4.2.2.
LED Circuit and KEY Input Circuit
Circuit Operation:
A drive pulse wave, as in Fig. 1, is output by IC1. That signal goes through the drive digital transistor and connects the key button
and LED cathode. By pressing the key, the drive pulse wave is input to KEYIN[0] ~ KEYIN[11]. In order to light the appropriate LED,
the LED control port is turned ON. That result LED is lit by the pulse driver.
and LED cathode. By pressing the key, the drive pulse wave is input to KEYIN[0] ~ KEYIN[11]. In order to light the appropriate LED,
the LED control port is turned ON. That result LED is lit by the pulse driver.
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