Panasonic KX-T7740X (serv.man2) Service Manual ▷ View online
9.2. DATA COMMUNICATION CIRCUIT
Function:
The data communication circuit serves the following functions:
Information exchanger between the PBX and DSS console and key input information as well as data for the LED control, etc. This
information is exchanged continuously at all times.
The data communication circuit serves the following functions:
Information exchanger between the PBX and DSS console and key input information as well as data for the LED control, etc. This
information is exchanged continuously at all times.
Circuit Operation:
When the DSS console receives an IRQ signal from the PBX, after it sends the key input information (19 pulses) to the PBX and
receives the data (47 pulses) for the LED control, etc. , the DSS console will return an acknowledge signal to the PBX.
When the DSS console receives an IRQ signal from the PBX, after it sends the key input information (19 pulses) to the PBX and
receives the data (47 pulses) for the LED control, etc. , the DSS console will return an acknowledge signal to the PBX.
1) Reception
The data from the DSS console is received via the H and L line along the path shown below.
The data from the DSS console is received via the H and L line along the path shown below.
H, L Line
→ D1 → T1 → R6 → Q2 → IC2 → IC1 Pin 18
2) Transmission
The data to the DSS console is transmitted along the following path.
The data to the DSS console is transmitted along the following path.
IC1 Pin 12
→ IC2 → Q1 → T1 → D1 → H, L Line
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KX-T7740X-B
9.3. LED CIRCUIT
The LED executes dynamic lighting for the status indicators, and control is executed by the output ports terminal name of IC1, D5,
D9~11, R70, R22, R30, R32, R40, R42, R60, R62.
D9~11, R70, R22, R30, R32, R40, R42, R60, R62.
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9.4. KEY INPUT CONTROL CIRCUIT
Sequential input information is executed by dynamic scanning.
The ports terminal name of IC1, D5, D9~11, R70 of IC1 or brought to High status consecutively.
If a key is pressed, the key-in information input is executed by ports terminal name of IC1, R72, R73, R80~83, R90~93.
The ports terminal name of IC1, D5, D9~11, R70 of IC1 or brought to High status consecutively.
If a key is pressed, the key-in information input is executed by ports terminal name of IC1, R72, R73, R80~83, R90~93.
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10 TROUBLESHOOTING GUIDE
10.1. NO OPERATION
10.2. LED DOSE NOT LIGHT
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