232

Communication ICs

BA6569AS / BA6569AFP

FCircuit operation

The BA6569AS and BA6569AFP carry out the following

basic operations.

(1)

Handset talk and receive

Voice signals received from a telephone line are output

to a handset speaker. Voice signals from the handset mi-

crophone are also output to the telephone line.

(2)

DTMF send and key tone input

The BA6569AS and BA6569AFP have a mute switch

which can be switched between a “handset send and re-

ceive” mode and a “DTMF send and key tone input”

mode by an external logic signal. In the “DTMF send and

key tone input” mode, it transmits DTMF signals from the

dial pad to the telephone line, and key tones to the hand-

set receiver.

(3)

AGC

Gain is adjusted steplessly in response to the size of cur-

rent from the telephone line. When there is a large cur-

rent (a short distance is involved), the gain is lowered.

The gain volume can also be adjusted by changing the

value of the resistor connected to the AGC pin.

(4)

Manual pad

In order to accommodate situations such as a PBX,

where there is little current but a short distance is in-

volved, the gain can be lowered by a constant volume re-

gardless of the current value. Fluctuation in the amount

of gain can be adjusted by changing the value connected

to the MPAD pin.