Panasonic KX-DT321UA Service Manual ▷ View online
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KX-DT321UA/KX-DT321UA-B
4.2.3.
LED Circuit
The lighting of the LEDS is controlled by pin 14 to 18 (Row) and pin 8 to 13 (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-DT321UA/KX-DT321UA-B
4.2.4.
Reset Circuit
Reset Signal is outputted from IC7 and inputted into IC2, IC3 and IC6 when the TEL cord is plugged in.
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KX-DT321UA/KX-DT321UA-B
4.2.5.
Power Supply Circuit
Power to the digital telephone set is provided from the PBX.
D.C. voltage is fed via a split transformer (T1) to diode bridge D1.
D.C. voltage is fed via a split transformer (T1) to diode bridge D1.
The PSU circuit includes a switching regulator (IC1) to produce the +3.3V output rail.
Q4 control the power supply circuit to prevent IC1 from starting up until the PBX feeds a 40V supply to the set (some other sets
work at 15V). They reduce the current consumption whilst the PBX is applying 15V, allowing the PBX to progress to 40V supply.
Q4 control the power supply circuit to prevent IC1 from starting up until the PBX feeds a 40V supply to the set (some other sets
work at 15V). They reduce the current consumption whilst the PBX is applying 15V, allowing the PBX to progress to 40V supply.
• Input voltage 21V or less
→ Q4 Off → IC1 pin 2 High → IC1 Off.
• Input voltage 21V or more
→ Q4 On → IC1 pin 2 Low → IC1 On.
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KX-DT321UA/KX-DT321UA-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 36) built in IC2 through Pulse Trans T1. The threshold voltage
of the comparator is determined by R101 to 103 and inputted to pin 37 and 35 of IC2.
The data to PBX is outputted from pin 38 and 39 of IC2, drives T1 by Transistor Q1 and transmitted.
of the comparator is determined by R101 to 103 and inputted to pin 37 and 35 of IC2.
The data to PBX is outputted from pin 38 and 39 of IC2, drives T1 by Transistor Q1 and transmitted.
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