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VOCON Board
Detailed Theory of Operation 7
Introduction This section of the manual provides a detailed circuit description of an
ASTRO Digital SABER VOCON (Vocoder/Controller) Board. When
reading the theory of operation, refer to your appropriate schematic
and component location diagrams located in the back section of this
manual. This detailed theory of operation will help isolate the
problem to a particular component. However, first use the ASTRO
Digital SABER Portable Radios Basic Service Manual to troubleshooting
the problem to a particular board.
General The VOCON board consists of two subsystems:
• vocoder
• controller
Although these two subsystems share the same printed circuit board
and work closely together, it helps to keep their individual
functionality separate in describing the operation of the radio.
The controller section is the central interface between the various
subsystems of the radio. It is very similar to the digital logic portion of
the controllers on many existing Motorola radios. Its main task is to
interpret user input, provide user feedback, and schedule events in the
radio operation, which includes programming ICs, steering the
activities of the DSP and driving the display.
The vocoder section performs the functions which previously were
performed by analog circuitry. This includes all tone signaling,
trunking signalling, and conventional analog voice, etc. All analog
signal processing is done digitally utilizing a DSP56001. In addition it
provides a digital voice plus data capability utilizing VSELP or IMBE
voice compression algorithms. Vocoder is a general term used to refer
to these DSP based systems and is short for voice encoder.
In addition, the VOCON board provides the interconnect between the
microcontrol unit (MCU), DSP, and the encryption board on secure-
equipped radios.
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