Instruction manual

Hardware installation
19
850-164696 / A
2.8 Ethernet Data Network
The echo sounder computer and the GPT transceiver
communicate via a local area network interface of the Ethernet
type.
The original Ethernet version was standardised in 1978 by
Xerox Corporation, Intel Corporation and Digital Equipment
Corporation.
A 1/2-inch 50-ohm coax cable is used as the communication
backbone medium, and a number of computers are connected to
this backbone cable via a transceiver cable (15-pin Delta
connector in each end) and a ”vampire” transceiver clamped
onto the Ethernet coax. The communication rate is 10 Mbit/s.
Today this original Ethernet version is denoted the IEEE 802.3
10Base5 standard. The original 1/2-inch coax is typically
referred to as thick Ethernet, and the 15-pin Delta connector is
referred to as the AUI (Attachment Unit Interface). A number of
variations of this technology have emerged in recent years.
By replacing the 1/2-inch coax with a thinner BNC type 50-ohm
coax we arrive at the IEEE 802.3 10Base2 standard which is
commonlyreferredtoasthin Ethernet.
Yet another variation is to replace the coax with fibre-optic
cable.
The last variation to be described here is the IEEE 802.3
10BaseT standard which uses twisted pairs of wire in a star
topology. This variation is commonly referred to as a twisted
pair (TP) system. For small local area networks it is usually
possible to use just one type of Ethernet, though for larger
networks one often ends up with a mixed system. Transition
units from one type of system to another are available from
numerous suppliers.
Both AUI and TP connectors are available on the EK60 General
Purpose Transceiver (GPT). A standard Ethernet adapter
(plug-in board) is required on the Processing Unit computer.
Typically, this board also has both the AUI and the TP
connectors available.
An EK60 echo sounder system can contain more than one GPT
connected to the same network cable. The echo sounder and
other computer devices can co-exist on the data network without
disturbing each other. If you wishto connect only one GPT to
the echo sounder computer, you do not need to install a
complete data network cabling system. For a minimum
point-to-point link you only need a twisted pair cable where the
receive and transmit wires have been swapped.