NGT—Technical description (2010)
NGT Transceiver System Technical Service Manual 77
Codan Interconnect Bus transmit path
The CIB is an 8-wire bus that connects all the units in the system together:
• SYS AUDIO+/–: The audio is TDM balanced, as described in the previous section.
• 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 on the transceiver when the line is
grounded (see page 70, Power on).
• GND: Ground is the supply return wire and is connected to the negative terminal of
the battery.
RF unit—Audio Interface PCB transmit path
The Transmit TDM SYS audio from the CIB goes to IC7/B. IC7/B then converts the
push-pull audio to single-ended audio so that the correct audio channel is sampled by
IC6/D.
C21 is the hold capacitor, and IC7/A, IC8/A and IC8/B form a 5-pole Chebyshev
reconstruction filter with a nominal cutoff frequency of 3 kHz. The filtered audio then
goes to the Application Processor PCB via ADC AUX IN.
Drawing 04-03109
To Next Page
Loading...
Need help?
General
