Panasonic KX-DT346UA Service Manual ▷ View online
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KX-DT346UA/KX-DT346UA-B
4.2.3.
LED Circuit
The lighting of the LED is controlled by pin 19 to 28 (Row) and pin 11 to 16 (Colum) of IC2.
The LED lights up in a dynamic lighting system.
The duty ratio is 1/8 (ON time 1.5ms).
The LED lights up in a dynamic lighting system.
The duty ratio is 1/8 (ON time 1.5ms).
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KX-DT346UA/KX-DT346UA-B
4.2.4.
Reset Circuit
Reset Signal is outputted from IC3 and inputted into IC1 and IC2 at the connection of TEL cord.
4.2.5.
Power Supply Circuit
This circuit converts the voltage supplied from PBX into the power supply voltage of +3.3V by IC5 (Switching Regulator IC).
IC10 controls the power supply circuit as below to turn IC5 on in low consumption current at starting up.
IC10 controls the power supply circuit as below to turn IC5 on in low consumption current at starting up.
• Input Voltage approx. 20V or less
→ L →IC5 ON
• Input Voltage approx. 20V or more
→ Q5 C (Collector) HiZ→IC6 OFF
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KX-DT346UA/KX-DT346UA-B
4.2.6.
Data Communication
Function
The data communication circuit serves the following functions:
Information exchanger between PBX and proprietary telephone, key input information as well as data for the LED control, LCD
control, voice data, etc. This information is continuously exchanged at all times.
Information exchanger between PBX and proprietary telephone, key input information as well as data for the LED control, LCD
control, voice data, etc. This information is continuously exchanged at all times.
Circuit Operation
The data received from PBX is inputted to the comparator (pin 68) built in IC2 through Pulse Trans T1. The threshold voltage of
the comparator is determined by R19 to 21 and inputted to pin 67 and 69.
The data to PBX is outputted from pin 70 and 71 of IC2, drives T1 by Transistor Q1 and transmitted.
the comparator is determined by R19 to 21 and inputted to pin 67 and 69.
The data to PBX is outputted from pin 70 and 71 of IC2, drives T1 by Transistor Q1 and transmitted.
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KX-DT346UA/KX-DT346UA-B
4.2.7.
DXDP Communication
Function:
This circuit performs the same type of communication as between the DPT and PBX, but for a DXDP-compatible DPT con-
nected to the DXDP port.
In addition, power feed is also controlled.
nected to the DXDP port.
In addition, power feed is also controlled.
Circuit Operation:
The data to the slave DPT is output from pins 63 and 64 of IC2 and sent via the pulse transformer T2 to JK2.
The data from the slave DPT is sent through the pulse transformer and is input to the comparitor (pin 61) built into IC2.
The threshold of the comparitor is determined by R19 to R21, which is input into to pins 60 and 62 of IC2.
The data from the slave DPT is sent through the pulse transformer and is input to the comparitor (pin 61) built into IC2.
The threshold of the comparitor is determined by R19 to R21, which is input into to pins 60 and 62 of IC2.
Power is supplied to the Slave DPT by means of a constant current circuit Q3 and Q4 as below:
• IC2 pin 58 H: Constant current circuit ON.
• IC2 pin 58 L: Constant current circuit OFF.
• IC2 pin 57 H: 40mA feed (normal supply to attached Slave DPT).
• IC2 pin 57 L: 20mA feed (initial supply to Slave DPT).
• IC2 pin 58 L: Constant current circuit OFF.
• IC2 pin 57 H: 40mA feed (normal supply to attached Slave DPT).
• IC2 pin 57 L: 20mA feed (initial supply to Slave DPT).
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