Samsung RS2544 Service Manual page 41

Circuit Descriptions
The step signals of DC 11∼ 12V will be generated periodically. If a sink signal outputs from IC4, DC 11-12V will be
applied to the LED input terminal and sink the LED output terminal to 0V. Therefore, LED will be ON for 2 miliseconds.
2) Key Scan
The 6 step signals, Q6∼Q4 are applied to scan the 6 keys (buttons). When SW6 is pressed, the step signal from Q6
will be reduced to 5V and entered to the MICOM, then MICOM will match a corresponding function for SW6 key.
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