Kyocera KM-3035 Service Manual page 322

2FD/2FF/2FG
The operation unit PCB (OPCB) consists of the operation unit left PCB (OPCB-L) and the operation unit right PCB (OPCB-
R).
The operation unit right PCB (OPCB-R) consists of key switches and LEDs. The lighting of LEDs is determined by scan
signals (SCAN5 to SCAN8) and LED lighting selection signals (DIGLED7 to DIGLED8) from the main PCB (MPCB). The
key switches operated are identified by the scan signals (SCAN5 to SCAN8) and the return signals (DIGKEY4 to
DIGKEY9).
As an example, to light LED 1 (L1), the LED lighting selection signal (DIGLED7) should be driven low in synchronization with
a low level on the scan signal (SCAN5). LEDs can be lit dynamically by repeating such operations.
As another example, if KEY 1 is pressed, the corresponding key switch is turned on feeding the low level of the scan signal
(SCAN5) back to the main PCB (MPCB) via the return signal (DIGKEY4). The main PCB (MPCB) locates the position where
the line outputting the scan signal and the line inputting the return signal cross, and thereby determines which key switch
was operated.
The operation unit left PCB (OPCB-L) consists of key switches and LEDs. The lighting of LEDs is determined by scan
signals (SCAN1 to SCAN4) and LED lighting selection signals (DIGLED1 to DIGLED6) from the main PCB (MPCB). The
key switches operated are identified by the scan signals (SCAN1 to SCAN4) and the return signals (DIGKEY1 to
DIGKEY3).
As an example, to light LED 7 (L7), the LED lighting selection signal (DIGLED1) should be driven low in synchronization with
a low level on the scan signal (SCAN1). LEDs can be lit dynamically by repeating such operations.
As another example, if KEY 23 is pressed, the corresponding key switch is turned on feeding the low level of the scan signal
(SCAN1) back to the main PCB (MPCB) via the return signal (DIGKEY1). The main PCB (MPCB) locates the position where
the line outputting the scan signal and the line inputting the return signal cross, and thereby determines which key switch
was operated.
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