Page 37 - DCAP311_DCAP607_WIRELESS_NETWORKS

Unit 2: Wireless System Architecture

z z Two-way radio Notes
z z Professional
In professional two-way radio systems, a base station is used to maintain contact with a dispatch
fleet of hand-held or mobile radios, and/or to activate one-way paging receivers. The base
station is one end of a communications link. The other end is a movable vehicle-mounted radio
or walkie-talkie. Examples of base station uses in two-way radio include the dispatch of tow
trucks and taxicabs.

Figure 2.8: Two-way Radio Systems

Source: http://en.wikipedia.org/wiki/Base_station
Basic base station elements used in a remote-controlled installation. Selective calling options such
as CTCSS are optional.

Professional base station radios are often one channel. In lightly used base stations, a multi-
channel unit may be employed. In heavily used systems, the capability for additional channels,
where needed, is accomplished by installing an additional base station for each channel. Each
base station appears as a single channel on the dispatch center control console. In a properly
designed dispatch center with several staff members, this allows each dispatcher to communicate
simultaneously, independently of one another, on a different channel as necessary. For example,
a taxi company dispatch center may have one base station on a high-rise building in Boston and
another on a different channel in Providence. Each taxi dispatcher could communicate with taxis
in either Boston or Providence by selecting the respective base station on his or her console.\

In dispatching centers it is common for eight or more radio base stations to be connected to a
single dispatching console. Dispatching personnel can tell which channel a message is being
received on by a combination of local protocol, unit identifiers, volume settings, and busy
indicator lights. A typical console has two speakers identified as select and unselect. Audio from
a primary selected channel is routed to the select speaker and to a headset. Each channel has a
busy light which flashes when someone talks on the associated channel.
Base stations can be local controlled or remote controlled. Local controlled base stations are
operated by front panel controls on the base station cabinet. Remote control base stations can be
operated over tone- or DC-remote circuits. The dispatch point console and remote base station
are connected by leased private line telephone circuits, (sometimes called RTO circuits), a DS-1,
or radio links. The consoles multiplex transmit commands onto remote control circuits. Some
system configurations require duplex, or four wire, audio paths from the base station to the
console. Others require only a two-wire or half duplex link.

LOVELY PROFESSIONAL UNIVERSITY 31