JK-CPU FC7.820.505

The JK-CPU FC7.820.505 (usually Version V1.0 or V1.1) is the Central Processing Unit board for the same specialized telephone exchange system as the previous boards you mentioned.

While the .507 handles the tone/interface logic and the .506 handles DTMF decoding, the JK-CPU is the “master” board that runs the system software, manages database memory, and coordinates all other modules.

The Full System Hierarchy

These three boards typically plug into a common backplane or rack to form a complete Marine or Industrial PABX (Private Automatic Branch Exchange):

Key Technical Features of the JK-CPU

• Processor Core: Contains the main Microcontroller (MCU) that executes the exchange’s instruction set.

• Configuration Storage: Likely contains an EPROM or Flash memory chip where the specific system settings (extension numbers, ring groups, etc.) are stored.

• System Status: Typically features LED indicators that show “Run,” “Fault,” or “Communication” status to help technicians diagnose system-wide failures.

• Power Requirements: Usually operates on a DC 12V or 5V rail provided by the JK-POWER board.

Critical Maintenance Note

If your entire phone system is “dead” (no dial tones, no lights on any extensions), the JK-CPU is the most likely culprit. However, if the CPU board’s “Run” light is blinking but you can’t dial out, the fault is more likely in the JK-DTMF (.506) or JK-TONE (.507).

[!CAUTION]

Data Loss: Because this is the CPU board, replacing it with a surplus unit may reset your extension configurations or system settings to factory defaults unless you can swap the memory chips from the old board to the new one.