Panasonic KX-DT321UA Service Manual ▷ View online
9
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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KX-DT321UA/KX-DT321UA-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 33 and 34 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 31) built into IC2.
The threshold of the comparitor is determined by R101 to R103, which is input into to pins 30 and 32 of IC2.
The data from the slave DPT is sent through the pulse transformer and is input to the comparitor (pin 31) built into IC2.
The threshold of the comparitor is determined by R101 to R103, which is input into to pins 30 and 32 of IC2.
Power is supplied to the Slave DPT by means of a constant current circuit Q5 and Q6 as below:
• IC2 pin 28 H: Constant current circuit ON.
• IC2 pin 28 L: Constant current circuit OFF.
• IC2 pin 27 H: 40mA feed (normal supply to attached Slave DPT).
• IC2 pin 27 L: 20mA feed (initial supply to Slave DPT).
• IC2 pin 28 L: Constant current circuit OFF.
• IC2 pin 27 H: 40mA feed (normal supply to attached Slave DPT).
• IC2 pin 27 L: 20mA feed (initial supply to Slave DPT).
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