L3914A中文资料意法半导体数据手册PDF规格书

DESCRIPTION

The device consists of the speech and the dialer. It provides the DC line interface circuit that terminates the telephone line, analog amplifier for speech transmission and necessary signals for either DTMF or loop disconnect (pulse) dialing.

SPEECH CIRCUIT

■ 2 TO 4 WIRES CONVERSION

■ PRESENT THE PROPER DC PATH FOR THE LINE CURRENT AND THE FLEXIBILITY TO ADJUST IT AND ALLOW PARALLEL PHONE OPERATION

■ PROVIDES SUPPLY WITH LIMITED CURRENT FOR EXTERNAL CIRCUITRY

■ SYMMETRICAL HIGH IMPEDANCE MICROPHONE INPUTS SUITABLE FOR DYNAMIC ELECTRET OR PIEZOELECTRIC TRANSDUCER

■ ASYMMETRICAL EARPHONE OUTPUT SUITABLE FOR DYNAMIC TRANSDUCER

■ LINE LOSS COMPENSATION

■ INTERNAL MUTING TO DISABLE SPEECH DURING DIALING

■ HOLD FUNCTION FOR PARALLEL PHONE WITH 400ms DELAY TO PREVENT FALSE RELEASE

DIALER CIRCUIT

■ 32 DIGITS FOR LAST NUMBER REDIAL BUFFER

■ 18 DIGITS FOR 13 MEMORY REDIAL

■ ALLOW MIXED MODE DIALING IN EITHER TONE OR PULSE MODE

■ PACIFIER TONE PROVIDES AUDIBLE INDICATION OF VALID KEY PRESSED IN A BUZZER OR/AND IN THE EARPHONE

■ TIMED PABX PAUSE

■ FLASH INITIATES TIMED BREAK: MASK OPTIONS WITH 585ms,300ms,100ms

■ CONTINUOUS TONE FOR EACH DIGIT UNTIL KEY RELEASE

■ USES INEXPENSIVE 3.579545MHz CERAMIC RESONATOR

■ POWERED FROM TELEPHONE LINE, LOW OPERATING VOLTAGE FOR LONG LOOP APPLICATION