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Functional Description
1.2.2
Line Levels
Using the RSS it is possible to independently adjust the receive and transmit nominal levels between
0 dBm and -13 dBm.
If automatic gain is selected via the RSS, the default value of -13 dBm is assumed.
1.2.3
Two or Four Wire Operation
To ensure operational flexibility, the TRICK is capable of interfacing with either a two-wire or four-
wire system (selected via the RSS).
See the Installation and Programming Guide for connector pin-outs.
1.2.4
TRC Signalling
The TRICK supports the Motorola Tone Remote Control (TRC) signalling protocol. The TRC protocol
consists of five distinct categories of individual tones;
High Level Guard Tone
Low Level Guard Tone
Console Commands
Acknowledgement
Status Reports
The High Level Guard Tone (HLGT) precedes a Function Tone and indicates a forthcoming
command. The following frequencies may be assigned to the HLGT via the RSS;
♦
2100 Hz
♦
2175 Hz
♦
2325 Hz
♦
3250 Hz
The HLGT is referenced as +6 dB to nominal, with a fixed duration of 120 ms.
The Low Level Guard Tone (LLGT) is transmitted by the control console after the Function Tone for
as long as the console PTT is pressed. The LLGT drives the PTT on the TX radio and informs any
other control consoles linked in parallel that the line is busy (see the Centro Plus Product Manual for
further details). The LLGT has the same frequency as the HLGT but is referenced at -24 dB to
nominal.
The guard tones should be selected carefully to avoid clashes with the particular 5-tone signalling
standard being used. The recommended guard tone frequencies are shown below.
Std, French & Modified ZVEI
70 & 100 mS CCIR, EEA
1-8
Table 1-2 Guard Tone Frequencies
5-Tone System
Guard Tone Frequency
2100 Hz
2325 Hz
Functional Description & Applications
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