Codan Interconnect Bus Receive Path; Junction Box Receive Path - Codan NGT 2010 RF Technical & Service Manual

NGT—Technical description (2010)
The output from the DSP (DAC-OUT) is filtered by IC2/B and IC2/A. It is then sampled
by IC1/B and IC1/C and becomes another audio channel on the CIB. The user can select
either raw audio or this enhanced audio via the handset. The channel switching is
performed in the junction box.

Codan Interconnect Bus receive path

The CIB is an 8-wire bus that connects all the units in the system together:
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Junction box receive path

Time division multiplex audio reconstruction and audio amplifier
Drawing 04-03201, or
Drawing
The push-pull system audio is converted to single-ended audio by IC8/A. The
synchronisation pulse is detected by V1 and fed to IC1 to synchronise the audio
channels. IC9/D and IC9/C sample the audio channels depending on requirements. Each
audio path has a 5-pole Chebyshev reconstruction filter comprising IC4, IC5 and IC6,
with a nominal cutoff frequency of 3 kHz.
One audio path goes via the volume control IC2/E and IC7/B, which is microprocessor
controlled from the speaker volume keys on the handset. This signal then goes to the
audio power amplifier IC3, which drives the loudspeaker.
The other audio path goes to the GPIO port for auxiliary equipment.
92
SYS AUDIO+/–: The audio is TDM balanced (see
audio generation).
SYS DATA+/–: The data uses CAN protocol. This protocol has good error-detection
capabilities and performs well in high-noise environments. The data rate on the CIB
is 125 kbps.
STBY: Standby power is a 100 mA, 6 V DC continuous supply. This is used to
backlight the key at night.
A PROTECTED: The Protected A rail is an unregulated battery supply that is used
to supply power to all the units in the transceiver system. The maximum current that
this can supply is 2 A. If very long runs of the CIB cabling are required, an external
supply may be connected to the junction box to supply power locally.
PWR ON: The power on line is used to switch the transceiver on when the line is
grounded (see page 70, Power
GND: Ground is the supply return wire and is connected to the negative terminal of
the battery.
04-03423
page 91, Time division multiplex
on).
NGT Transceiver System Technical Service Manual