DOWNLOAD Panasonic KX-TS85GB / KX-TS85GW Service Manual ↓ Size: 1.62 MB | Pages: 34 in PDF or view online for FREE

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•¡ 

Function:
The tone dialing circuit consists of a DTMF (Dual Tone Multi Frequency) signal generator (outputted from Pin 12 of the
IC1) for tone dialing, and also a circuit for outputting the signal to line.
The DTMF circuit identifies inputs from the 12 keys (1,2,3,4,5,6,7,8,9,0,

•–

and #) by means of a total of seven frequencies,

that is four low frequencies (Low group) and three high frequencies (High group).

Circuit Description:
When a dial key is pressed, a DTMF signal is output from Pin 12 of IC1 as an analog synthetic wave.
The signal flow to the line is as follows.
Pin 12 of IC1 

•¨

 Q6 

•¨

 R18 

•¨

 Q4 

•¨

 Tel Line.

The DTMF signal is sent to the line via the following path. Q6 is an amplifier which is used to output the signal to line.
Following is the signal flow used to output the DTMF signal from the handset as a monitor tone when a dial key is
pressed.
Pin 21 of IC1 

•¨

 R32 

•¨

 C28 

•¨

 Handset Speaker.

The signal combination and frequency correspoonding the each dial key is shown in p23.

Note:
The circuit diagram may be modified at any time with the development of new technology.

•¡ 

When the hook switch S1 is ON (off-hook), the circuit is closed, and current is supplied to the base of Q3 via the diode
bridge D4 and Q3 is On 

•¨

 Q4 is ON (OFF-HOOK condition).

Q4 and Q3 are the dial pulse generating circuits, and are driven by the DIALER (IC1), when the DIALER Pin 2 of IC1 is
LOW 

•¨

 Q3 is OFF and Q4 is OFF. (break)

If port Pin 2 is HIGH 

•¨

 Q3 is ON 

•¨

 Q4 is ON. (make)

MIC

SPEAKER

Key
Board
Switch

EEPROM

DIALER

DTMF

Output and Control

Circuit

SP Amp

Q3,Q4

Q1,Q2

Q6

D4

Dial Pulse
Switch
and
On/Off
Control

Diode

Bridge

C1

C2

R1

R2

D1

IC1

H/S

MIC

SPEAKER

Handset
Amp
Receiving
Transmitting
and
Address
Signal

T

R

S1

Transmit

Amp

Diode

Bridge

DC-DC

CONVERTER

C45

IC2

Tone

Ringer

Circuit

R1

R3

R4

D1

R10

R11

R13

R15

R14

SI-2

R16

Q4

D7

R19

R20

R21

R7

C10

R9

Q2

Q1

D6

L2

D8

C14

D5

POS1

ZNR2

JACK1

R12

R5

R18

C1

R2

D2

D3

D15

D14

C2

C6

D4

3

4

2

1

C7

C5

C8

C11

C13

2

3

4

5

B

Ring

Tip

A

SI-1

Pin 2 of
   IC1

Q3

•|

23

•|

C28

R32

C27

21

14

12

Q6

IC1

T

R

Q4

Q3

R15

R14

R18

T

R

R1

C72

C1

R2

R7

Q2

Q1

R3

C5

C8

C10

D2

D6

D1

D14

D15

D3

D5

L2

R4

R9

R58

R5

C14

L5

C37

27

31

25

22

26

FCI

VPP

VDD

LS1

CM

D8

       

D9

D11

Q8

D16

Low Group

Frequencies

High Group

Frequencies

L1

L3

L4

697 Hz 

•}

1.5%

L2

770 Hz 

•}

1.5%

852 Hz 

•}

1.5%

941 Hz 

•}

1.5%

H1

H3

H2

1209 Hz 

•}

1.5%

1336 Hz 

•}

1.5%

1477 Hz 

•}

1.5%

1

4

7

•–

2

5

6

0

3

6

9

#

L1

L2

L3

L4

H1

H2

H3

•¡ 

Circuit Operation:
The bell signal passes through C1 (R1) 

•¨ 

supplying power to pin 26 and 22 of IC1. (Q1, Q2 is DC-DC converter.)

 signal input to pin 31 of IC1.

The ring signal is outputted from Pin 27 of IC1, and its volume is adjusted in 3 steps (H-M-L) by programming then impressed
on the speaker, and so is generated.

    D1 . . . . . . . . . . . . . Bell sensitivity adjustment

•¨

•|

24

•|

•¡ 

Function:
This circuit controls the automatic switching of the transmitted and received signals, to and from the telephone line,
when the unit is used in the hands-free mode.

Circuit Operation:
The Speakerphone can only provide a one-way communication path.
In other words, it can either transmit an outgoing signal or receive an incoming signal at a given time, but cannot do
both simultaneously. Therefore, a switching circuit is necessary to control the flow of the outgoing and incoming
signals. This switching circuit is contained in IC1 and consists of a Voice Detector, Tx Attenuator, Rx Attenuator,
Comparator and Attenuator Control. The circuit analyzes whether the Tx (transmit) or the Rx (receive) signal is louder,
and then it processes the signals such that the louder signal is given precedence.
The Voice Detector provides a DC input to the Attenuator Control corresponding to the Tx signal.
The Comparator receives a Tx and a Rx signal, and supplies a DC input to the Attenuator Control corresponding to
the Rx signal. The Attenuator Control provides a control signal to the Tx and the Rx Attenuator to switch the
appropriate signals on and off. The Attenuator Control also detects the level of the volume control to automatically
adjust for changing ambient conditions.

1) Transmission Signal Path
The input signal from the microphone is sent through the circuit via the following path:
• Mic 

•¨

 Pin 7 and 9 IC1 

•¨

 Pin 12 of IC1 

•¨

 Interface (Q6) 

•¨

 R18 

•¨

 Telephone Line.

2) Reception Signal Path
Signals received from the telephone line are outputted at the speaker via the following path:
• Telephone Line 

•¨

 C22 

•¨

 Pin 15 of IC1 

•¨

 Pin 21 of IC1 

•¨

 Pin 19 of IC1 

•¨

 Pin 27 of IC1 

•¨

 Speaker.

3) Control Signal Path
Control signals for transmission and reception are inputted to IC1 via the following path:

Transmission Control Signal Path: Fixed (inside IC1)
Reception Control Signal Path: Telephone Line 

•¨

 C22 

•¨

 Pin 15 of IC1 

•¨

 Pin 21 of IC1 

•¨

 Pin 20 of IC1.

R18

C22

R19

R56

C45

Q6

R48

MIC

SPEAKER

C38

R53

C46

R52

C37

L5

R50

C39

C40

CS

IC1

RI

R0

RECV

RECVI

LS1

M4 M3

C60

12

15

21

19
20

27

9

7

(     )