Ian Waugh - A Mariner\'s Guide to Marine Communications

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9 Printer

Inmarsat-A and Inmarsat-B installations

2 The Main Control Unit (MCU): referred to as the Below Deck Unit

(BDU) in some equipment, the MCU/BDU performs a similar

function to the modulator/de-modulator in an SSB radio - combining/
separating your voice, fax, telex or data signal with the carrier
frequencies.
3 Junction Box: a physical interface between the various input devices
(telephone, fax machine, computers for telex and/or data, etc.) and
the MCU/BDU. Telephone handsets, fax machines and/or computers
may also be connected directly to the MCU in some installations.
4 Telephone Handset: a Single telephone handset will be the minimum
requirement on all Inmarsat-A/B installations. A typical Inmarsat-A
unit will have one telephone, one fax/computer and one telex/

computer connected - only one of which can be used at anyone

time. Inmarsat-B installations can have up to six telephone/computer!
fax interfaces and one telex interface - but only one can be used at a
time (unless 'multiplexed' into a large antenna).
5 Telephone/Telex Distress Button: reqUired on all Inmarsat-B
G MD SS installations. This button initiates a Distress Priority

MARINE COMMUNICATIONS 165