ST3917A Datasheet, PDF (1/16 Pages) STMicroelectronics – SPEECH - TONE/PULSE DIALER - LED INDICATOR

ST3917A
ST3917B
SPEECH - TONE/PULSE DIALER - LED INDICATOR
..SPEECH CIRCUIT
2 TO 4 WIRES CONVERSION
PRESENT THE PROPER DC PATH FOR THE LINE
.CURRENT AND THE FLEXIBILITY TO ADJUST IT
ANDALLOWPARALLEL PHONE OPERATION
SYMMETRICAL HIGH IMPEDANCE MICRO-
PHONE INPUTS SUITABLE FOR DYNAMIC,
ELECTRET OR PIEZOELECTRIC TRANSDUCER
.ASYMMETRICAL EARPHONE OUTPUT SUIT-
ABLE FOR DYNAMIC TRANSDUCER
.LINE LOSS COMPENSATION FIXED INTER-
NALLY BY A.G.C.
.INTERNAL MUTING TO DISABLE SPEECH
DURING DIALING AND EXTERNAL MUTING
.TO DISABLE TRANSMIT AMPLIFIER DURING
CONVERSATION MODE
LED INDICATOR EITHER FOR KEYBOARD ILLU-
MINATION (OR ON-LINE INDICATION) DURING
DIALING AND CONVERSATION OR FOR TONE
MODE INDICATION, THROUGH MU/MFI PIN
.DIALER CIRCUIT
STORE UP TO 32 DIGITS FOR LAST NUMBER
..REDIAL BUFFER, LNR IS INHIBITED IF THERE
ARE MORE THAN 32 DIGITS STORED
ALLOWMIXED MODE DIALING IN PULSE MODE
PACIFIER TONE PROVIDES AUDIBLE INDI-
CATION OF VALID KEY PRESSED IN A BUZZ-
ER OR/AND IN THE EARPHONE
._{TIMED PABX PAUSE / 10PPS PULSE RATE}
._{MAKE/BREAK RATIO : 40/60 (ST3917A) AND}
33/67 (ST3917B)
._{4 SELECTABLE OPTIONS ON FLASH DURA-}
.^{TION AND SOFTSWITCH INHIBITION IN ONE}
OF THE OPTION WITH 100ms FLASH TIMING
2 SELECTABLE OPTIONS : TRANSMIT MUTE
TOGETHER WITH LED FOR KEYBOARD ILLUMI-
NATION OR LED FOR TONE MODE INDICATION
.CONTINUOUS TONE FOR EACH DIGIT UNTIL
KEY RELEASE
.USES INEXPENSIVE 3.579545MHz CERAMIC
RESONATOR
.POWERED FROM TELEPHONE LINE, LOW
OPERATING VOLTAGE FOR LONG LOOP AP-
PLICATION
DESCRIPTION
The device consists of the speech and the dialer func-
tions. It provides the DC line interface circuit that termi-
nates the telephone line, analog amplifier for speech
transmission and necessary signals for either DTMF
and pulse dialing. When mated with a tone ringer, a
complete telephonecan be producedwith just two ICs.
TheDClineinterfacecircuit developsits ownlinevoltage
acrossthedeviceandit is adjustableby externalresistor
to suit different country’s specification. A built-in LED
driver can deliver excess line current to external LED
indicator(s) during dialing and speech mode. The
LED(s) can be used either for keyboard illumination
purpose or for tone mode indication during softswitch
and mixed mode dialing by connecting MU/MFI pin to
VDDandGND oranyrowrespectively.The LEDcurrent
is limited to 17mA (typical).
The speech network provides the two to four wires inter-
face,electronic switchingbetweendialingandspeechand
automaticgain control on transmit and receive.
The dialing network buffers up to 32 digits into the LND
memorythatcan be laterredialedwith asinglekeyinput.
Users can store all 13 signalling keys and access
several unique functions with single key entries. These
functions include : Pause, Last Number Dialled (LND),
Softswitch and Flash. (see Figure 1).
The FLASH key simulates a hookflash to transfercalls
or to activate other special features provided by the
PABX or central office.
The PAUSE key stores a timed pause in the number
sequence. Redial is then delayed until an outside line
can be accessed or some other activities occur before
normal signalling resumes. A LND key automatically
redials the last number dialed.
Adedicatedpin MU/MFI is used to select the muting for
transmit amplifier and lighted dial LED for keyboard
illumination or a LEDindicator for tonemode indication.
The SEL pin allows selection of any one of the four
possible Flash duration options.
DIP28
(Plastic Package)
ORDER CODES :
ST3917AN - ST3917BN
SO28
(Plastic Package)
ORDER CODES :
ST3917AD - ST3917BD
July 1996
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