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Raider Installation and Operation Rev. 1.4.2
The COMM PORT (Communications Port) carries RS-232 signals between the Raider and the modem
or computer. The Raider side of this interface is called DTE (Data Terminal Equipment) and connects
directly to any DCE (Data Communication Equipment) device. A modem is a DCE device.
Direct Connection to Computer
Both, the Raider and the PC are DTE devices and will not communicate with each other on a 1 to
1 (straight through) cable. When connecting the Raider directly to a computer for testing or
programming, a null modem cable must be used. The null modem cable swaps Pins 2 & 3 (send
and receive) in its connection from the computer to the Raider. The only connections needed for
most computers are pins 2 RX Data, 3 TX Data and 5 Circuit Ground.
The Raider uses the TELEVIDEO 920 terminal emulation commands. Please configure your
computer terminal program to TVI-920. If your current program does not have this emulation,
Trident recommends the T-Comm Communications program or other compatible program such as
ProComm Plus
®
. The display may appear distorted if the proper emulation mode is not selected.
About Modems
A "modem" (
mo
dulator-
dem
odulator) is a device that converts RS-232 signals to tones that can
be passed over telephone lines. This allows digital communication devices like the Raider to send
information from a remote site to your local phone line. As key strokes are entered on your
keyboard the computer converts them to
ASCII
data (
A
merican
S
tandard
C
ode for
I
nformation
I
nterchange). The ASCII data is then converted to a serial bit stream similar to the data that goes
back and forth between the mobile and trunk system. This serial bit stream is converted to a series
of RS-232 voltage levels that are fed into the modem (+12 volts = 1 and -12 volts = 0). The modem
sends a different tone for each voltage level it receives (2200Hz for 1 and 2100Hz for 0).
When the modem on the "other end" sends a character, two more frequencies are introduced into the
communication stream so that data can be passed in "full duplex" (both directions, simultaneously). The
sending modem converts these tones into RS-232 voltage levels and passes them to your computer. The
computer decodes the ASCII data and displays it on the screen as characters for you to read.
A dial-up phone line at the remote site, a modem connected to the Raider and a modem capable
of auto-dialing connected to your computer are required in order to make remote contact with the
Raider. The modem at the Raider site should be set to "auto answer". When you want to
communicate with the Raider, you must instruct the modem connected to your computer to dial the
phone line connected to the Raider's modem. When the Raider's modem sees the ringing it will
answer the phone and start the data communication between your computer and the Raider.
Certain modems tend to behave unreliably under the adverse conditions sometimes occurring at
a radio site (unreliable AC power, lightning and extreme temperatures). For those reasons, Trident
recommends using the Trident Tuff-Modem at all radio sites. The Tuff-Modem is controlled by
a special microprocessor which is much more reliable under the extremes of site conditions. The
Tuff-Modem re12v DC and may be supported by the Raider's power supply.
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