Le79228
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•
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Internal ringing signal
12- or 16-kHz metering signal
A low-level voltage proportional to the voice signal (VOUT
i
)
A voltage that controls longitudinal offset for test purposes (VLB
i
)
Data Sheet
The Le79228 Quad ISLAC device performs the codec and filter functions associated with the four-wire section of the subscriber
line circuitry in a digital switch. These functions involve converting an analog voice signal into digital PCM samples and converting
digital PCM samples back into an analog signal. During conversion, digital filters are used to band-limit the voice signals.
The user-programmable filters set the receive and transmit gain, perform the transhybrid balancing function, permit adjustment
of the two-wire termination impedance and provide frequency attenuation adjustment (equalization) of the receive and transmit
paths. Transhybrid balancing is also included. All programmable digital filter coefficients can be calculated using WinSLAC™
software. The PCM codes can be either 16-bit linear two’s-complement or 8-bit companded A-law or µ-law.
Besides the codec/filter functions, the Le79228 Quad ISLAC device provides all the sensing, feedback, and clocking necessary
to completely control VE790 series ISLIC device functions with programmable parameters. System-level parameters under
programmable control include active loop current limits, feed resistance, and feed mode voltages.
The Le79228 Quad ISLAC device supplies complete mode control to the VE790 series ISLIC device using the control bus and
(P1-P3) tri-level load signal (LD
i
).
The Le79228 Quad ISLAC device provides extensive loop supervision capability including off-hook, ring-trip and ground-key
detection. Detection thresholds for these functions are programmable. A programmable debounce timer is available that
eliminates false detection due to contact bounce.
For subscriber line diagnostics, AC and DC line conditions can be monitored using built in test tools. Measured parameters can
be compared to programmed threshold levels to set a pass/fail bit. The user can choose to send the actual PCM measurement
data directly to a higher level processor by way of the voice channel. Both longitudinal and metallic resistance and capacitance
can be measured, which allows leakage resistance, line capacitance, and telephones to be identified.
*Note:
"i" denotes channel number
OPTIONAL VCP FEATURES
Optional Voice Control Processor (VCP) features provide the following solutions to the VE790 series intelligent chip sets:
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Integrated test software routines
DTMF detection
Aggregated codec/filter control
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Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
