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2.2
Network Media Installation — Local Line
Overview
Local Line Cable
Characteristics
2-4
Network Installation
TIWAY I is a multi-drop communications network. It consists of a main
trunk cable (the "spine") and dropline cables. The network can connect up to
248 secondaries to a host computer.
NOTE: Although addresses can range from 1 to 254 on TIWAY I, addresses
248 through 254 cannot be used because of the limitations of the Modbus
protocol.
The selection of the media interface depends primarily upon two criteria:
the distance to be spanned and the cost of installation. The main trunk can
be up to 25,000 feet long, and each dropline can be up to 100 feet long, with
Local Line. For distances exceeding 25,000 feet, the use of RS-232-C media
interfaces and modems is required.
If cable redundancy is required (two TIWAY I cables), you will need two
Gateways, two cables, and two host system interface devices. Refer to the
appropriate host system user manuals for more specific information on
redundant connections.
The TIWAY I Local Line is a physical signalling technique (baseband,
differential current drive) which operates over shielded, twisted-pair
cabling. The Local Line cable may be up to 25,000 feet long. The Local Line
uses tap housings to simplify the addition of connections onto TIWAY I.
The Local Line is designed to operate with shielded twisted-pair cable which
has a characteristic impedance of 124 ohms. The interface is a male, 9-pin
D-type connector with pin assignments as shown in Table 2-1.
Table 2-1 Pin Assignments for Local Line Connector
Pin
Name
1
2
3
Shield
4
5
6
LLM+
7
8
9
LLM–
Description
Reserved
Reserved
Cable shield and signal common
Reserved
Reserved
Positive biased signal line
Reserved
Reserved
Negative biased signal line
TIWAY I Gateway User Manual
- Quick Links:
- Introduction
- The Gateway Interface
- Interface Ports
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