Theory of Operation: Tone Remote Control Board
24 6881086C22-B
Figure 8. Remote Key-Up
0 indicates OFF state of S100 (8-5) 0101-1111 indicates same as Standard Table
1 indicates ON state of S100 (8-5)
During an LPTT function, the LLGT is removed from the transmitted audio path
by a notch filter on the TRC board. This notch filter is tuned to the guard tone
frequency (2175 Hz).
When not in the LPTT mode, the TRC board accepts receiver audio from the
ASTRO radio, passes it through a notch filter (tuned to guard tone), and then
through a line driver for transmission down the wireline to the remote console.
The receive notch filter prevents false HLGT detection due to possible receiver
audio components near the guard tone frequency (since on a two-wire board,
receiver audio output and transmit audio/tone inputs are tied together at the
wireline).
HLGT
Time
FT LLGT
40 ms
120 ms
Amplitude
Voice
Table 12. TRC Function Tone Descriptions
Function
Tone
Tone Table Description
0000 - Standard
Table
0001
CentraCom II
0010
No Mode Select
0011
Mode 1 Only
0100
No Mode 1
2175 Hz Guard Tone/PTT Guard Tone/PTT Guard Tone/PTT Guard Tone/PTT Guard Tone/PTT
2050 Hz Monitor Monitor Monitor Monitor Monitor
1950 Hz Mode 1 Select Mode 1 Select No effect Mode 1 Select Mode 2 Select
1850 Hz Mode 2 Select Mode 2 Select No effect No effect Mode 2 Select
1750 Hz Mode 7 Select Mode 7 Select No effect No effect Mode 7 Select
1650 Hz Mode 8 Select Mode 8 Select No effect No effect Mode 8 Select
1550 Hz Mode 5 Select Mode 5 Select No effect No effect Mode 5 Select
1450 Hz Mode 6 Select Mode 6 Select No effect No effect Mode 6 Select
1350 Hz Mode 3 Select Mode 3 Select No effect No effect Mode 3 Select
1250 Hz Mode 4 Select Mode 4 Select No effect No effect Mode 4 Select
1150 Hz Secure Coded
Select
Mode 5 Select Secure Coded
Select
Secure Coded
Select
Secure Coded
Select
1050 Hz Secure Clear
Select
Mode 6 Select Secure Clear
Select
Secure Clear
Select
Secure Clear
Select
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