DESCRIPTION (continued)

When mated with a tone ringer, a complete tele-

phone can be produced with just two ICs.

The DC line interface circuit develops its own line

voltage across the device and it is adjustable by

external resistor to suit different country’s specifi-

cation.

The speech network provides the two to four

wires interface, electronic switching between dial-

ing and speech and automatic gain control on

transmit and receive.

The dialing network buffers up to 32 digits into the

LND memory that can be later redialed with a sin-

gle key input. Additionally, another 13 memories

(including 3 emergency memories) of 18 digits

memory is available. Users can store all 13 sig-

nalling keys and access several unique functions

with single key entries. These functions include:

Pause/Last Number Dialed (LND), Softswitch,

Flash.

The FLASH key simulates a timed hook flash to

transfer calls or to activate other special features

provided by the PABX or central office.

The PAUSE key stores a timed pause in the num-

ber sequence. Redial is then delayed until an out-

side line can be accessed or some other activity

occurs before normal signaling resumes.

A LND key input automatically redials the last

number dialed.

FUNCTION PIN DESCRIPTION

C1, C2, C3, C4, R5, R4, R3, R2, R1

Keyboards inputs. Pins 1, 2, 3, 4, 24, 25, 26, 27,

28. The one chip phone interfaces with either the

standard 2-of-9 with negative common or the sin-

gle-contact (Form A) keyboard.

BLOCK DIAGRAM

L3916A

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