Operating Instructions Part 2

2 OEM Series™ I/O Guide MDS 05-3624A01, Rev. B
Modem Speeds
Two modem speeds are available in the OEM 900 transceiver—
standard 9600, and an optional 4800 bps. The latter provides 3 dB of
extra receive sensitivity where greater range is required.
Changing the modem speed requires loading different software into the
radio using MDS’ Radio Configuration Software. See Radio
Programming Methods on Page 14 for more information.
Frequency Coverage
The OEM 900 Series radio operates in the 900 MHz frequency band.
The exact frequency coverage of each model is listed in the
Specifications chart on Page 26.
NOTE: The radio’s frequency range (band) cannot be set or changed
by the user; it is set at the factory.
1.2 Applications
Point-to-Multipoint, Multiple Address Systems (MAS)
Point-to-multipoint (MAS) is the most common application of the
transceiver. It consists of a central master station and several associated
remote units as shown in Figure 2. An MAS network provides
communications between a central host computer and remote terminal
units (RTUs) or other data collection devices. The operation of the radio
system is “transparent” to the computer equipment. That is, the radio
system transports the data in its original form, making no changes to the
data format.
Often, the radio system is used to replace a network of remote monitors
currently linked to a central location by leased telephone lines. At the
central office of such a system, there is usually a large mainframe
computer and some means of switching between individual lines
coming from each remote monitor. In this type of system, there is a
modulator/demodulator (modem) at the main computer and at each
remote site, usually built into the remote monitor itself. Since the cost of
leasing a dedicated-pair telephone line is quite high, radio is frequently
used as an alternative communication medium.