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Am79574
Subscriber Line Interface Circuit
DISTINCTIVE CHARACTERISTICS
s Programmable constant resistance feed s Line-feed characteristics independent of battery variations s Programmable loop-detect threshold s On-chip switching
regulator for low-power dissipation s Pin for external ground-key noise filter capacitor available s Ground-key detect option available s Two-wire impedance set by single external impedance s Polarity reversal feature s Tip Open state for ground-start lines s Test relay driver optional s On-hook transmission
BLOCK DIAGRAM
(TIP) A
Ring Relay Driver Test Relay Driver
RINGOUT TESTOUT C1 C2 C3 C4 E1 E0 DET GKFIL VTX RSN
HPA
Ground-Key Detector ...