SECTION III PRINCIPLES OF OPERATION - TM-11-5830-263-20-P0023

TM-11-5830-263-20&P

SECTION III PRINCIPLES OF OPERATION

1.12.

GENERAL OVERVIEW OF SYSTEM OPERATION

Refer to TM 11-5830-263-10, Chapter 1, Section 1, paragraph 1.10 for general overview of system

operation.

1.13.

POWER DISTRIBUTION

Power enters the MCS through the power connector and an Electromagnetic Compatibility (EMC) filter,

which also provides reverse polarity and transient-spike protection. From this point, the power supply

circuitry is split into two individual supplies: (1) the VIS regulated dc power supply, and (2) the ANR

isolated power supply. Both power supplies provide identical power conditioning circuitry. This

conditioning circuit provides overvoltage, undervoltage, and overcurrent protection. In the case of over

(40Vdc) or under (15Vdc) voltages occurring, the circuit shuts off power to the system until the voltage

returns to within the system's operating range. If the circuitry senses excessive amps from its power

supply, the overcurrent electronic circuit breaker for that power supply will trip, removing power. This is

detected by an internal circuit within the MCS and indicated on the MCS's POWER FAULT LED

(SYSTEM or ANR) display as being an overcurrent condition. To reset either circuit breaker, the SYSTEM

switch on the MCS is turned to "off" then back to one of the "on" positions.

The regulated system power supply provides +5Vdc and -5Vdc for the MCS internal circuitry and supplies

power to the other VIS modules via the highway cables.

The ANR power supply provides a +24Vdc regulated voltage that is connected into the system highway to

power the ANR modules in the headsets.

The PTT switch on the headset, set in the momentary position for transmission over a selected radio, has

a maximum input voltage and current of 35Vdc and 50 mA.

1.14.

DATA TRANSMISSION

The system component parts function to allow integration of vehicle crew internal communications and

radio communication in a ring bus configuration. The system communication scheme, Time Division

Multiple Access (TDMA), is synchronized by the MCS. VIS appends 1 of 32 destination addresses to

each byte of digital data. Of these 32 addresses, 16 have been allocated for up to 8 radios (1 for transmit

and 1 for receive for each radio), 4 have been allocated for intercom, 1 for control, with 11 addresses

remaining as spares for future system growth. (VIS currently uses a maximum of 6 radios.) The MCS

regulates the timing of the digital packets of information, which may be initiated from any other station

except the MOS. The MOS can receive audio information but cannot transmit. The distribution of audio

(intercom) to the MOSs is achieved in an analog format; however, the audio power amplification is

individually controlled at each MOS to prevent volume fluctuations when crewmembers connect or

disconnect their headsets. This approach also isolates the headsets from the audio source, increasing the

survivability of the system if a particular headset becomes damaged or short-circuited. The FFCS allows

an operator full access to all radio and intercom communications and provides the operator with

microphone keying options. Each RIT interfaces with two radios. When multiple RITs are connected to

the ring bus, up to six radios can be interfaced. This includes the two radios interfaced to the MCS. The

MCS and RIT convert analog radio signals from analog to digital and place the packets of information on

the bus, which allows the commander and crew to select the digitized audio information in various

combinations. They also convert FFCS audio from digital to analog for transmission over the radios. The

FFCS then selects which packets of radio information it requires and converts the digitized audio to

analog. The FFCS also communicates over the intercom to maintain internal communication between

crewmembers and communicates to the MCS and RIT for external radio traffic.

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