Service Manual

Page 1.11
2 ~ SERVICE PHILOSOPHY
Simplex
Mode of operation whereby the radio operates as a conventional fixed channel
radio outside the Trunking network.
Squelch
System used to prevent weak, unintelligible signals and random noise from being
heard by a radio operator while still allowing intelligible signals to be received
normally. This is accomplished by the use of a threshold below which any received
signals are ignored. Only signals whose signal-to-noise ratio is above the squelch
level cause the audio circuits of the radio to be enabled, with the result that only
satisfactory signals are received. The squelch level is specified in SINAD.
Star (*) digits
Digits known as Status or Message digits. These digits are used for three
purposes:
• Status Digits for Selcall Identities
• Wildcard digits in Status strings
• Use in DTMF dialled strings - their use is network dependent to access special
services.
Status
A feature whereby a radio's status (or usually the status of the radio's user) can be
transmitted and a status message from other radios can be displayed. This
operates through status digits in Selcall identities. Either in Encode Identities or
Decode Identities as follows:
Encode Identities: Status digits within the identity are used to transmit the current
situation of the radio's user (E.g. "Out To Lunch").
Decode Identities: Status digits are looked up in a table (Status Menu) for possible
messages to display.
SW
Software.
SYS
System Identity Code part of the CCSC.
TCXO
Temperature Compensated Crystal Oscillator.
Temporary
Temporary Registration; a process carried out by the Dispatcher due to some
system failure that prevents it from carrying out normal registration. The radios will
recognise this temporary registration mode but will otherwise use the network in
the same way as if they were registered. They may be required to re-register when
normal registration mode is resumed.
Three Tone Reset
This is a system whereby a call to a user automatically reset all other users in a
group.
Example: a call to user '12345' would call 12345 and reset all other users on this
channel with an identity 123nn where n can be any digit 0-9, A-F.
Timed Reset
Facility that causes the Radio, after a certain period of time, to restore current
channel to its initial condition e.g. if it was previously searching it will resume
searching.
Time Shared
A time-shared control channel is one that is used by more than one site. This
allows a wide coverage area to be obtained using only one frequency.
The forward channel from the TSC to the radio is divided into timeslots. Each site
using the channel is allocated one timeslot in which to transmit and send
signalling.
Therefore, when on a timeshared channel, the radio may be able to receive bursts
of signalling from different sites at different signal strengths and may receive
periods when no signalling is received.
Depending on the type of system, the radio may be able to perform transactions
with any site it can receive from or only with a specific site.