2241A Distribution Panel
OPERATION
Section 3
3 - 2
transmitters at all sites except one for purposes of
testing the one site. In this case, operation of the PTT
Switches insures which transmitters will remain OFF and
which transmitter will be keyed - independent of
commands that the dispatch console may give. This
provides an opportunity to test both the “Talk Out” and
“Talk In” equipment without interference from other
transmitters.
This technique can also be used to keep a channel open
for testing in situations where the dispatch console
imposes a time limit on transmissions. In some
simulcast systems, equalizers are required to match the
phase and amplitude responses of “talk out” links to
each site. This requires that the response of the links to
each site be measured. In order to do this, one site is -
in turn -made operational and all interfering sites are
turned off.
All simulcast systems require the transmission delay to
each site be measured so that individual audio delay
lines can be precisely adjusted. Delay lines are set so
that audio delay from multiple sites is the same in those
geographical areas where transmitter coverage overlap.
Typically this is done by measuring the “Round Trip
(audio) Delay” to a test receiver, with one site active at a
time. The PTT Switches provide a convenient and sure
means of controlling this process.
3-5-2 TROUBLE SHOOTING
The PTT Switches can
be used for trouble shooting the network. Since
individual transmitters can be controlled, the PTT
Switches can be used to isolate a problem to a particular
site or base station. Once having isolated a problem
situation, that site or radio can be amputated by setting
it’s PTT Switch to DISABLE until repairs have been
made.
3-5-3 SPECIAL CASES / ADAPTATION.
PTT Switches
can also be used to rapidly adapt the network for special
situations. An alternate or backup site can be enabled in
the event a failure or accident at the primary site. A site
or a channel can be silenced to permit a neighboring
jurisdiction temporary use of a channel (frequency) to
handle a special situation.
FINAL NOTE
Features found in all Convex Products
are the result of feedback from current and prospective
customers. Please tell us what you would like improved
or changed. We appreciate your suggestions.
Please
check our website for the current address
and phone number.
www.convexcorp.com
e-mail: [email protected]
Phone 703-433-9901 / FAX 703-433-9904
CONVEX CORPORATION
1319 Shepard Drive
Sterling, VA 20164 USA
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Convex also manufactures precision audio delay
lines
( Models 2046 and VDL-2M Simulcast Delay Lines)
and Delay Measuring, TIMS Test Sets (Model 806A).
