LS656 Ver la hoja de datos (PDF) - STMicroelectronics

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Fabricante

LS656

TONE GENERATOR INTERFACE TELEPHONE SPEECH CIRCUIT WITH MULTIFREQUENCY

STMicroelectronics 

LS656

parator (8) of LS656 drives internal electronic

switches ; the voltage and the current delivered by

the voltage supply (9) are increased to allow the op-

eration of the oscillator.

This extra current is diverted by the receiving and

sending section of the LS656 and during this opera-

tion the receiving output stage is partially inhibited

and the input stages of sending and receiving am-

plifiers are switched OFF.

Figure 8 : Two to Four Wires Conversion.

A controlled amount of the signalling is allowed to

reach the earphone to give a feedback to the sub-

scriber ; the MF amplifier (10) delivers the dial tones

to the sending paths.

The mute function can be used also when a tempo-

rary inhibition of the output signal is requested. The

application circuit shown in fig. 10 fulfils the

EUROPE II standard (-6, -8 dBm). If the EUROPE I

levels are required (-9, -11 dBm) an external divider

Figure 9.

8/15

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