18 August 1998
a. Modulated RF data transmission systems can be used for UMCS with the installation of radio
receivers and transmitters (a combination receiver/transmitter is referred to as an RF transceiver). The
data signal enters a transmitter terminal where it modulates the RF carrier wave. After traveling through
through the communication media, the modulated RF carrier enters a receiver terminal where it is
amplified and demodulated back into the original data signal. Modems must be provided at each
receiver/transmitter location. Frequency modulation is used instead of amplitude modulation because it
b. RF systems can be effectively used for two-way communication between the island station and
field equipment panels where other communication media is not available or suitable for the application.
One-way RF systems can be effectively used to control loads at remote locations such as for unitary
heaters in warehouses and in family housing applications. The use of RF will be coordinated with the
a. Packet radio is a two-way data transmission method utilizing a protocol similar to the CCITT X.25
protocol used for packet data transmission over wirelines. Using this protocol, data can be transmitted
either on a single frequency dedicated for data transmission or on existing voice channels (although not
simultaneously with voice transmission). Networks can be established on a polling or report-by-
exception basis, or a combination of both.
b. Equipment required at each communication node for a packet radio data transmission system
include a packet modem and controller designed to be used with a radio, and an RF transceiver. The RF
transceiver, packet modem and controller may be separate or may be integrated into a single device.
8. GOVERNMENT-FURNISHED DATA TRANSMISSION SYSTEMS. For large installations, a
substantial portion of the cost of a UMCS is related to the physical installation of data transmission media
(wirelines or fiber optics). Depending on the extent, condition and availability of government-owned
communications infrastructure on an installation, the cost of the UMCS may be reduced through the use
of government-furnished data transmission systems. Coordination with the communications officer is
required to verify the reliability of the existing data transmission systems. The designer will determine and
show in the design the characteristics and extent of government-furnished transmission systems as well
as extensions, interfaces and equipment to be provided by the contractor to provide an operable system.