Technical Manual Issue 2.1 4000 Digital Series II
Page 72 STA0381
4.2.2 PDE 4621A - 16 Channel CODEC Card
Figure 67 - PDE4621A 16 Channel CODEC Card
The CODEC card is a 16-channel 16-bit analogue to digital and digital to analogue converter. Sampling
rate of 42.7kHz give a bandwidth of 17kHz. A control bus provides communication with a central
processor. The audio data input and output drive onto a multiplexed digital audio bus.
The card incorporates input gain control and there are voice detectors (VOXs) on each input. These
functions are both accessed via the control bus. The audio outputs are provided as differential voltage
outputs. Balanced analogue audio inputs and outputs are available via transformers on the PDE3622
CODEC RCU.
This card is fitted with 16 pre-set level controls that set the VOX signal detection threshold for each
analogue input. Where VOX operation is in use, these controls will be set up prior to shipping and should
need no further adjustment. The nominal threshold setting is -20dB. The level controls (single-turn
potentiometers) are mounted in two rows on the leading edge of the board, below the handle. The pots
are numbered and correspond to the inputs, but as a guide channel 1 is the top most pot. A standard
pot-trimming tool can be used to adjust them. The VOX threshold range is -40dB to 0dB.
Sub-fitted versions of this card are used in the smaller 4400 matrices. The channel capacity is from 2
to16 analogue inputs and outputs, in pairs.
A block diagram of the CODEC card is shown below.
For a description of the functioning of the LEDs on the card refer to the
4000 Installation Guide.
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