Lorain Electronics Great Lakes Automated VHF System
Based on information in a 1982 LEC publication
The Lorain Electronics Great Lakes
Automated VHF System was composed of fourteen remotely controlled
VHF-FM stations (Map)
strategically located to provide ship-to-shore coverage for large
commercial vessels on all but Lake Ontario. While primarily
designed to operate with automatic full duplex radio-telephones capable
of direct dialing land telephones and ships it also operated with
non-automatic push-to-talk equipment.
Normal
ranges over open water for large vessels to a shore station were from
40 to 75 miles, for smaller vessels, from 20 to 35 miles.
The
fourteen VHF stations were each connected to the national land
telephone network via a regular subscriber business line to the nearest
telephone central office. This is the circuit over which all
telephone calls were made whether directly dialed by the vessel or by
the control center operator. LEC furnished the ships with a
Great Lakes Marine Telephone Directory (from which this article is
derived) which listed the local exchange numbers and the prefixes that
could be dialed as local numbers through each station. In
addition, each station was connected to the control center at WMI in
Lorain, Ohio, by another special leased circuit over which control
signals, data information and operator voice communications were
made. Leased circuits were very expensive and to make the
system economically viable it was necessary to connect three or four of
the stations to each of the four leased lines.
At
each station a mini computer, or electronic brain, controlled the
station functions and temporarily stored call information until
released to the master computer at the Lorain control center.
The
master computer at Lorain polled each station on each of the four
control circuits once every two seconds. The information was
in the form of data and only took a fraction of a second to
send. The computer sorted the information received into
various categories such as incoming manual ship or land calls that
signaled the operator, billing information that was to be stored, or
various checks on the condition of the station equipment.
Portions of the information were displayed on a screen for visual
inspection
by the operator.
When the control center operator
used a control line to talk to a ship through one of the stations, the
other stations on that line could not be polled and thus no call
alarms, etc., could be sent to the control center until the operator
released the line to the computer. For this reason ships may
have experienced delays in reaching the control center when making a
manual call to one of the other stations on the same control
line. Direct dial calls were, not affected and the ships were
urged to use that method whenever possible.
Weather
broadcasts, storm warnings, hydro-graphic reports, etc., required the
use of the control lines and polling could not be done until the
broadcast was completed. Weather broadcasts were normally
made at scheduled times and customers were cautioned to avoid making
calls that overlapped into the broadcast times as they would likely be
cut off when the broadcast began.
This system was sold to WJG-Maritel in 198(?),
and they closed it in 1990 due to lack of traffic. Some of
the stations were then sold to WLC.
