Service Manual

Page 1.8
2 ~ SERVICE PHILOSOPHY
DSP
Digital Signal Processor.
DTMF
Abbreviation of Dual Tone Multi-Frequency signalling. Used to dial into Telephone
networks using tone dialling.
Dual Watch
A facility that enables the Radio to periodically monitor another channel for a signal
above squelch. Typically applications are checking an emergency channel whilst
on another channel.
Economiser
A process by which the Receiver is powered down whilst there is no received
signal. Periodically the receiver is powered up to check for such a signal. This is
used to extend the battery life of a Portable.
Enabled
The 'True' state of a parameter. That indicates this parameter is active. Typically
this state is represented by a mark (either a tick or a cross) in a check box.
Compare with Disabled.
Encode
Transmission of signalling. Either Selcall where Selcall tone digits are encoded
into tone frequencies or CTCSS/DCS where tones modulated onto the channel's
carrier.
ETS
European Technical Standard.
Fallback
A mode of operation that may be entered when the Network is suffering a
malfunction. During this mode certain facilities (e.g. PSTN) may not be available.
FFSK
Fast Frequency Shift Keying. This is a signalling system for the transfer of digital
information. It works by using one of two audio tones to represent data being
transmitted.
Fleet
A group of units formed such that only a shortened form of dialling (2 or 3 digits) is
required between them. These groups are normally assigned contiguous Idents.
FOACSU
Full Off Air Call Set Up. A method of call set-up where the calling party has to
manually answer the incoming call before the trunking system will allocate a traffic
channel to the call. This reduces the loading on traffic channels as it prevents them
being allocated to calls when the called party is not present to deal with the call.
PLA
Programmable Logic Array.
FPP
Field Personality Programmer.
Hash (#) digits
These digits are used for two purposes:
• For Selcall identities (encode and decode) - known as User Id digits. These digits
are replaced by the user id entered at switch on (if enabled)
• Use in DTMF dialled strings - their use is network dependent to access special
services.
IDENT
A 13 bit number used for Identification purposes. Associated with a Prefix (PFIX)
this forms a 20 bit address which is used for identification purposes in signalling
between the radio and the trunking system.
Identity
Name given to a sequence of tones that is used in sequential tone signalling. See
Valid Selcall Digits.
Idle State
The state of the radio when it is not in a call.
Inaccessible
A state of a channel such that it is unavailable to the user through normal methods
of channel selection. Therefore inaccessible channels will not appear on the
channel menu.
Include Calls
These types of calls are used to allow a 3rd party to join into an existing call.