Panasonic KX-DT321UA Service Manual ▷ View online
10
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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KX-DT321UA/KX-DT321UA-B
4.2.8.
Analogue Circuit
This circuit performs the setting of call paths and volume adjustment in each mode of operation, via IC4.
Audio gain settings are downloaded serially from IC6, which obtains its information from the PBX.
Audio gain settings are downloaded serially from IC6, which obtains its information from the PBX.
• IC4 sends PCM audio data (Rx) to IC3 (Digital speakerphone chip) via a PCM interface.
• IC4 receives PCM audio data (Tx) from IC3 via a PCM interface.
• DTMF-like tone (from key-press, etc) is input to IC4 in analogue form.
• IC4 receives PCM audio data (Tx) from IC3 via a PCM interface.
• DTMF-like tone (from key-press, etc) is input to IC4 in analogue form.
1. Handset call:
Transmit signal is input from handset microphone. Pin 57 of IC6 drives analogue switch (IC9) to connect handset microphone
to the signal path. The signal is amplified by an internal amplifier within IC4
to the signal path. The signal is amplified by an internal amplifier within IC4
→ A/D conversion within IC4 → Gain adjustment
(within IC4)
→ sent to PBX via IC3 and IC2 as PCM data.
Receive signal arrives from PBX
→ IC2 → IC3 → D/A conversion from PCM data by IC4→ Gain adjustment by DSP of IC4 →
amplified by 1st amp of IC11
→ output from L52 to the earpiece of the handset.
2. Speakerphone call:
When in speakerphone mode, only a one-way communication path is provided at any given time. IC3 compares the transmit
and receive PCM signals during speakerphone mode, and then provides a one-way communication path, dependant on which
end has the greatest audio content.
Transmit signal is input from the Speaker-phone microphone into IC4. The signal is amplified by an internal amplifier within
IC4
and receive PCM signals during speakerphone mode, and then provides a one-way communication path, dependant on which
end has the greatest audio content.
Transmit signal is input from the Speaker-phone microphone into IC4. The signal is amplified by an internal amplifier within
IC4
→ Gain adjustment within IC4→ sent to PBX via IC3 and IC2 as PCM data.
Receive signal arrives from PBX
→ IC2 → Gain adjustment by IC3 → D/A conversion from PCM data by IC4 → pin 24 of IC4
→ pin 27 of IC4 → pin 28 of IC4 → pin29 of IC4 → output from pin 3 and 4 of IC4 to directly drive the speaker.
3. Headset call:
Transmit signal is input from headset microphone. Pin 57 of IC6 drives analogue switch (IC9) to connect headset microphone
to the signal path. The signal is amplified by an internal amplifier within IC4
to the signal path. The signal is amplified by an internal amplifier within IC4
→ A/D conversion within IC4 → Gain adjustment
(within IC4)
→ sent to PBX via IC3 and IC2 as PCM data.
Receive signal arrives from PBX
→ IC2 → IC3 → D/A conversion from PCM data by IC4→ Gain adjustment by DSP of IC4 →
amplified by 2nd amp of IC11
→ output from L54 to headset.
Speech is prevented from being received by handset by IC6 pin 58 output, which drives base of Q51 (ON) which applies mute
to the handset receive path (when handset is on-hook during call using the headset).
to the handset receive path (when handset is on-hook during call using the headset).
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