SL1062A

System Logic

Semiconductor

SLS

Automatic gain control input AGC

Automatic line loss compensation is achieved by

The automatic gain control varies the gain of the

microphone amplifier and the receiving amplifier in

accordance with the DC line current. The control

range is 5.8 dB which corresponds to a line length of

5 km for a 0.5 mm diameter twisted-pair copper cable

with a DC resistance of 176

Ω/km and average

attenuation of 1.2 dB/km. Resistor R6 should be

chosen in accordance with the exchange supply

voltage and its feeding bridge resistance (see

Table 1).

Table 1 Values of resistor R6 for optimum line-loss

compensation at various values of exchange supply

voltage

and

exchange

feeding

bridge

Ω.

400

Ω)

600

Ω)

800

Ω)

1000

Ω)

R6(K

Ω)

36

100

78.7

-

-

48

140

110

93.1

82

60

-

-

120

102

The ratio of start and stop currents of the AGS curve

is independent of the value of R6. If no automatic

line-loss compensation is required the AGS pin may

be left open-circuit. The amplifiers, in this condition,

will give their maximum specified gain.

Sidetone suppression

signal in the earpiece. Maximum compensation is

obtained when the following conditions are fulfilled:

R9 x R2 = R1 x

=

(2)

It fixed values are chosen for R1, R2, R3 and R9, then

condition

(1)

will

always

be

fulfilled

when

R8//Z

bal

<<R3.

To obtain optimum sidetone suppression, condition

(2) has to be fulfilled which results in:

Where k is a scale factor; k =

The scale factor k, dependent on the value of R8, is

chosen to meet the following criteria:

• compatibility with a standard capacitor from the

• Z

<<R3 fulfilling condition (a) and thus

ensuring correct anti-sidetone bridge operation

• Z

>>R9 to avoid influencing the transmit

gain.

therefore be for an average line length thus giving

optimum setting for short or long lines.

MAXIMUM RATINGS

*

Symbol

Parameter

Condition

Min

Max

Unit

Positive continuous line voltage

-

12

V

Repetitive line voltage during

switch-on or line interruption

-

13.2

V

Repetitive peak line voltage for a

1 ms pulse per 5 s

R9 = 20

Ω; R10 = 13 Ω;

see Fig.5

-

28

V

Line current

R9 = 20

Ω

-

140

mA

positive input voltage

-

V

negative input voltage

-

-0.7

V

Total power dissipation

R9 = 20

Ω; note 1

-

666

mW

Tstg

Storage temperature

-40

+125

°C

Functional operation should be restricted to the Recommended Operating Conditions.

°C) and a maximum junction

temperature of 125

°C.

R8

R1

R8

R1

Input voltage on all other pins