Panasonic KX-TCD958RUC Service Manual ▷ View online
6.1.6. FACTORY SERIAL PORT (SEE Fig. 19)
In order to communicate with the handset during manufacture and servicing (using a PC) a serial data link has been provided.
Serial data input/output is provided on J102 (TP151), and a ground is provided on J103. The bi-directional serial data line is split
into two at IC101 pin 27 (input) and pin 26 (output). Data rate is 9600 baud. D105 provides ESD protection, and R117 and C146
provide RF de-coupling.
Serial data input/output is provided on J102 (TP151), and a ground is provided on J103. The bi-directional serial data line is split
into two at IC101 pin 27 (input) and pin 26 (output). Data rate is 9600 baud. D105 provides ESD protection, and R117 and C146
provide RF de-coupling.
6.1.7. AUDIO PATH-RX AUDIO-LINE INPUT (SEE Fig. 20)
Audio from the Line Interface TXAF (TP123) enters the BBIC on pin 58. R111 and C113 are to balance the line input amplifier, into
the ADC part of the codec, where it is sampled and turned into digital data. The burst mode controller then processes this raw data
(called the B-field) performing encryption and scrambling, adding the various other fields that go together to produce the GAP
standard DECT frame, assigning to a time slot and channel etc. The data then passes through the gaussian filter to emerge on pin
22 as TRADAT, (TP132).
the ADC part of the codec, where it is sampled and turned into digital data. The burst mode controller then processes this raw data
(called the B-field) performing encryption and scrambling, adding the various other fields that go together to produce the GAP
standard DECT frame, assigning to a time slot and channel etc. The data then passes through the gaussian filter to emerge on pin
22 as TRADAT, (TP132).
6.1.8. AUDIO PATH - TX AUDIO - LINE OUTPUT (SEE Fig. 20)
Audio from the receiver RECDAT enters the BBIC on pin 20 and passes through the clock recovery circuit. The burst mode
controller separates out the B-field data, and performs de-encryption and de-scrambling as required. It then goes to the DAC part
of the codec where data is turned back into analogue audio. The audio signal is amplified by the gain-controlled line output
amplifier, and balanced audio is output on pin 63, and fed as RXAF (TP120) to the Line Interface.
controller separates out the B-field data, and performs de-encryption and de-scrambling as required. It then goes to the DAC part
of the codec where data is turned back into analogue audio. The audio signal is amplified by the gain-controlled line output
amplifier, and balanced audio is output on pin 63, and fed as RXAF (TP120) to the Line Interface.
Circuit Diagram
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KX-TCD958RUC
6.2. THE LINE INTERFACE SECTION
6.2.1. INTRODUCTION
This section consists of the telephone line interface, bell detector, hookswitch, pulse dialing circuits, audio circuits, DC mask & line
impedance circuits, power supplies, and battery charger circuits.
impedance circuits, power supplies, and battery charger circuits.
6.2.2. TELEPHONE LINE INTERFACE (SEE Fig. 21)
The telephone line is connected (via 2 or 3 jumpers selected for country of destination) to a bridge rectifier D8. Surge suppressor
SA3 protects against excessive line voltages. Test points are TP14 (A), TP13 (B). Bridge rectifier D8 provides for lines of either
polarity. The output of D8 is “Line +” (TP50) and “Line -” which is ground.
SA3 protects against excessive line voltages. Test points are TP14 (A), TP13 (B). Bridge rectifier D8 provides for lines of either
polarity. The output of D8 is “Line +” (TP50) and “Line -” which is ground.
6.2.3. BELL DETECTOR (SEE Fig. 21)
The AC ringing signal is detected by optocoupler IC2, using its internal diode in conjunction with D4. DC from the line is blocked
by C2. The other components D2, D3, and R3 reduce current and increase the circuit impedance in line with national requirements.
When ringing is detected IC2 will turn on, and the RING line (TP76) will be dragged to a low voltage.
by C2. The other components D2, D3, and R3 reduce current and increase the circuit impedance in line with national requirements.
When ringing is detected IC2 will turn on, and the RING line (TP76) will be dragged to a low voltage.
Circuit Diagram
Fig. 21
6.2.4. CLIP CIRCUITS (SEE Fig. 21)
The caller ID signal is detected by IC4.
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KX-TCD958RUC
6.2.5. HOOKSWITCH (AND PULSE DIALING) (SEE Fig. 22)
T8 is the hookswitch, driven by T9. When the phone is “off-hook”, the HOOK control signal from the BBIC will be a high logic level
(+3V), and both transistors will be on, thus T8 will “loop” the line. The zenner diode D10 protects transistor T13 against transient
line voltages.
(+3V), and both transistors will be on, thus T8 will “loop” the line. The zenner diode D10 protects transistor T13 against transient
line voltages.
6.2.6. PULSE DIALING (SEE Fig. 22)
During pulse dialing the hookswitch (T8, T9) is used to generate the pulses using the HOOK control signal, which is set high during
pulses. To force the line impedance low during the “pause” intervals between dial pulses, the PAUSE-DIAL signal turns on T11,
(increases current), thus reducing line impedance (see 8.3.10. BATTERY CHARGER)
pulses. To force the line impedance low during the “pause” intervals between dial pulses, the PAUSE-DIAL signal turns on T11,
(increases current), thus reducing line impedance (see 8.3.10. BATTERY CHARGER)
6.2.7. AUDIO CIRCUITS (SEE Fig. 22)
The line output signal from the BBIC RXAF is amplified by T13. The RXAF line is DC coupled to T13 thus making it work as a
current limiter (typically < 8mA). The emitter load of T13 is complex to achieve the correct frequency response, since the line load
is also complex. The line input signal TXAF is taken from the junction of R41 and R70. Phase cancellation of the line output audio
occurs at this point, so that only incoming line audio should be passed to the BBIC on TXAF.
current limiter (typically < 8mA). The emitter load of T13 is complex to achieve the correct frequency response, since the line load
is also complex. The line input signal TXAF is taken from the junction of R41 and R70. Phase cancellation of the line output audio
occurs at this point, so that only incoming line audio should be passed to the BBIC on TXAF.
Circuit Diagram
Fig. 22
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KX-TCD958RUC
6.2.8. POWER SUPPLIES (SEE Fig. 23)
The AC Adaptor for the KX-TCD953 / KX-TCD958 consists of two separate isolated DC supplies providing a +8 V supply for the
base circuitry, and a 9 V supply only for the charger circuit. The isolation is because the main base circuitry is connected to the
telephone line, so potentially hazardous voltages may be present, while the charger circuitry has charge contacts that could be
touched by the operator, so the two supplies must be kept separate. The 8 V supply from the AC Adaptor is connected via J2 pin
1 (TP90) +8 V, and J2 pin 2 (TP89) ground. The unregulated +8 V supply is fed to the first regulator.This regulator IC7 provides
a regulated output pin 2 (TP91) of +4.0 V (called +4V). The second regulator IC11 is fed with +4V and provides the stable +3.2V
supply (TP95). During power-up this regulator generates a RESET signal (TP94) which is used to reset the microcontroller and
BBIC.
base circuitry, and a 9 V supply only for the charger circuit. The isolation is because the main base circuitry is connected to the
telephone line, so potentially hazardous voltages may be present, while the charger circuitry has charge contacts that could be
touched by the operator, so the two supplies must be kept separate. The 8 V supply from the AC Adaptor is connected via J2 pin
1 (TP90) +8 V, and J2 pin 2 (TP89) ground. The unregulated +8 V supply is fed to the first regulator.This regulator IC7 provides
a regulated output pin 2 (TP91) of +4.0 V (called +4V). The second regulator IC11 is fed with +4V and provides the stable +3.2V
supply (TP95). During power-up this regulator generates a RESET signal (TP94) which is used to reset the microcontroller and
BBIC.
The regulator IC6 provides a regulated output pin 2 (TP109) of +6.0V.
6.2.9. BATTERY CHARGER (SEE Fig. 23)
The 9 V supply from the AC Adaptor is connected via J2 pin 6 (TP82) positive, and J2 pin 5 (TP78) negative. The constant current
battery charger circuit is made up of T14 and T15 (series pass transistor) and associated components. Charging detector circuit
T16 switches on when a charging current flows through R64 and D11, and turns on IC6. The charge contacts are connected via
J5. Charge current flows in via J5 (TP88), through T15, R63, AC ADAPTOR 9V supply, R64, D11, and out of J5 (TP84).
battery charger circuit is made up of T14 and T15 (series pass transistor) and associated components. Charging detector circuit
T16 switches on when a charging current flows through R64 and D11, and turns on IC6. The charge contacts are connected via
J5. Charge current flows in via J5 (TP88), through T15, R63, AC ADAPTOR 9V supply, R64, D11, and out of J5 (TP84).
Circuit Diagram
Fig. 23
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KX-TCD958RUC
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