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Mutual Aid Box Alarm System Communications Committee |
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| ADVOCACY STATEMENT #6 | ||||||||||||||||||||||||
| CTCSS Tones | ||||||||||||||||||||||||
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1.0 PURPOSE
To implement the use of Carrier Tone Coded Squelch Systems (CTCSS), also commonly known as “Private Line (TM)” or “PL(TM)” on the IFERN and fireground frequencies.
2.0 SCOPE
This policy applies to all MABAS member agencies. It is encouraged that all fire departments and related emergency response organizations throughout Illinois adopt the procedures set forth herein.
3.0 BACKGROUND
When the MABAS organization was formed in the early 1970’s, radio communications were primitive as compared to the systems and equipment in use today. Many radios were not capable of CTCSS and those that were CTCSS equipped were limited to a single tone frequency. Since numerous CTCSS tones were already in use throughout the Chicago metropolitan area, a single CTCSS tone for MABAS was not practical and carrier squelch mode was selected.
Radio spectrum has become increasingly congested, especially in the large metropolitan areas. This congestion includes the public safety radio frequency spectrum. Many base stations that monitor the IFERN frequency in carrier squelch mode are subjected to adjacent channel interference and frequency mixes. Adjacent states utilize the IFERN frequency for other purposes, which also cause unwanted interference. The result is radio volumes are muted, limiting the effectiveness of the frequency.
In the command unit environment, where multiple radios are being used in close proximity to one another, there is often unwanted noise received and sounded through the radio speakers. While mostly annoying, this problem can be masked by the use of different CTCSS tones on the various frequencies being used.
Most radio communications equipment in use today by the fire service is capable of multiple CTCSS tones, selected on a mode specific basis. Older equipment can also be inexpensively modified to transmit CTCSS tones.
4.0 POLICY/PROCEDURE
The MABAS Special Communications Committee hereby makes the following recommendations for both member and non-member Fire Departments:
4.1 All IFERN base station radios should be programmed or modified for transmit and receive CTCSS utilizing a tone frequency of 210.7 Hz (M2).
4.2 All fire service mobile/portable radios should be programmed or modified for transmit CTCSS utilizing the following tones:
4.3 All MABAS Divisions and fire departments should be prepared to implement the use of CTCSS on the IFERN frequency with an absolute application date of January 1, 2006.
4.4 All base and communications/command van users should monitor the frequencies in the carrier squelch mode prior to transmitting as required by FCC regulations.
5.0 CONCLUSION
Adding CTCSS to base station receivers should control unwanted co-channel and adjacent channel interference.
Approved by the MABAS Executive Board on 04/24/2003.
MABAS CTCSS Statement |
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