Intelligent Access™ Voice Solutions
Relay
Driver 1
R1
LD
Am79R251
Intelligent Subscriber Line Interface Circuit (ISLIC™)
DISTINCTIVE CHARACTERISTICS
a73 Monitor of two-wire interface voltages and
currents supports
— Voice transmission
— Through chip ring generation
— Programmable DC feed characteristics
— Independent of battery
— Current limited
— Selectable off-hook and ground-key thresholds
— Subscriber line diagnostics
— Leakage resistance
— Loop resistance
— Line capacitance
— Bell capacitance
— Foreign voltage sensing
— Power cross and fault detection
a73 Supports internal and external ringing
— High voltage operation supports long loops
a73 +5 V and battery supplies
a73 Dual battery operation for system power saving
— Automatic battery switching
— Intelligent thermal management
a73 Compatible with inexpensive protection
networks
— Accommodates low tolerance fuse resistors or
PTC thermistors
a73 Metering capable
— 12 kHz and 16 kHz
— Smooth polarity reversal
a73 Tip-open state supports ground start signaling
a73 Integrated test load switches/relay drivers
BLOCK DIAGRAM
Two-Wire
Interface
Signal
Transmission
Gain/Level Shift
Longitudinal
Control
Attenuator
Thermal
Management
Control
Fault
Meas
Signal
Conditioning
Switch
Driver
Relay
Drivers
Input Decoder and
Control Registers
Relay Control
AD
SA
BD
SB
HPB
HPA
TMN
TMP
VBL
VBH
R2
R3
RYE
TMS
VBP
IMT
ILG
VREF
VSAB
VLB
VTX
RSN
CREF
P3
P2
P1
Pub. # 22480 Rev: C Amendment: /0
Issue Date: December 1999
BGND VCCGND