Analog Interfaces; Dsp Module - Alcatel-Lucent OmniPCX NDDI2-2 Manual

Chapter
1
A/D and D/A voice signal conversion is ensured by 2 QLSLAC circuits. Each Quad Low
voltage Subscriber Line Audio - processing Circuit (QLSLAC) contains 4 coders-decoders
(CODECS) and supports 4 analog interfaces.
One Time Division Multiplex (TDM) or TS allocation connects both QLSLAC to circuit C1.
The QLSLAC acts as:
- an interface between :
• the Pulse Code Modulation (PCM) bus (Time-Slot Assigner (TSA)) and the processor,
• the SLIC OET/CET management and 4 Signal Processing Channels (SPC),
- the programmable software for transmission features (input impedance, reception and
transmission gains, echo cancellation, µ or A laws coding, etc.).
1.3.2

Analog interfaces

Analog interfaces:
- control the signalling,
- transmit voice,
- receive messages to identify the caller (CLIP), if any.
Interfaces are made up of the following parts:
- protection circuits which consist of:
• overvoltage protection circuits to avoid damage in case of any short circuit,
• EMI filtering circuits to reduce the RFI effects on the telephone line-card.
- impedance for ringing signal:
A firmware command allows a low or high impedance to be connected. This command
allows, with a specific equipment (country dedicated daughter board), either a ringing
impedance or a spark quench circuit to be connected (loop protection circuit during
dialing).
- loop circuits which can be:
• on line loop, a high dynamic impedance circuit with DC current limitation (compatible
with TBR21),
• dialing loop (very low resistance).
- loop current detector.
- polarity detector:
Still used for paging, its use depends on the country for NDDI operation. The polarity can
be detected only if a DC current loop is present.
- interface for AC signalling at hang-up:
The interface allows the AC signalling received during the hang-up phase to be transmitted
from the line to the QLSLAC (to be detected by the DSP). This signaling can be ringing,
dual tone (DT-AS), DTMF, V23 or Bell202 type for line call identification messages (CLIP
function).
1.3.3

DSP module

The Digital Signal Processing (DSP) module has the following functions:
1-4