MC34118

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

9 of 12

www.unisonic.com.tw

QW-R108-007,D

FUNCTIONAL DESCRIPTION(Cont.)

AGC

The AGC circuit only affects the circuit under such situation: when the circuit is in the receive mode, and when

the transmit and receive gains remains constant.

ATTENUATOR CONTROL BLOCK

This block has the seven:

* C1: The output of the comparator operated by RLO2 and TLO2 (here means in microphone/ speaker side).

* C2: The output of the comparator operated by RLO1 and TLO1 (here means Tip/ Ring side).

* C3: The output of the transmit background noise monitor.

* C4: The output of the receive background noise monitor.

* Volume control

* Dial tone detector

* AGC circuit

The C1~C4 effect is as follows:

INPUTS

C1

C2

C3

C4

OUTPUT

1

X

Transmit Mode

Y

Y

Fast Idle Mode

Y

Y

Fast Idle Mode

X

1

Receive Mode

0

X

Slow Idle Mode

0

0

Slow Idle Mode

0

0

Slow Idle Mode

X

0

Slow Idle Mode

Switching to the full transmit or receive from any other mode is at the fast rate (~30 ms).

X :Don’t care

Y :C3,C4 are not both 0