JVC 250 Service Manual page 59

Chapter 5---Electronics
I/O control for VIC selection
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Two RS-232 serial interface ports
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Infrared (IR) remote control interface. Accepts input from front or rear IR
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detectors.
External 3 color system status LEDs. Green indicates normal, yellow is
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standby and red indicates a fault condition.
External Service Mode Switch. Pressing this switch during a power-up
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sequence brings the system up in a diagnostic mode (for maintenance)
rather than a normal operating mode.
Figure 5-3 Rear of Electronics Module with rear cover and panel removed.
5-4 Model 250 Service Manual