E F Johnson Company 2425372 Benutzerhandbuch
Draft
-4 5300 ES Series Mobile Radio Operating Manual
December 2006
When “SQ Normal” is selected, the receiver unsquelches only if a carrier is detected.
Scanning and P25 NAC detection are not disabled with this mode selected. The selected
mode remains in effect until it is manually changed. Selecting another channel or cycling
power does not reselect a default condition. There is a programmable option to display
“MON” when the “SQ Normal” mode is selected.
Scanning and P25 NAC detection are not disabled with this mode selected. The selected
mode remains in effect until it is manually changed. Selecting another channel or cycling
power does not reselect a default condition. There is a programmable option to display
“MON” when the “SQ Normal” mode is selected.
5.4.2 Tone Call Guard Squelch
Tone-type Call Guard squelch utilizes subaudible CTCSS tones from 67-254.1 Hz.
Although there are 42 tones assigned, those above 33 (210.7 Hz) are normally not used
because of their close proximity to the voice band which starts at 300 Hz. In addition,
tones 11 (97.4 Hz), 39 (69.3 Hz), 40 (206.5 Hz), 41 229.1 Hz), and 42 (254.1 Hz) are
normally not used because they may cause interference with adjacent tones.
Although there are 42 tones assigned, those above 33 (210.7 Hz) are normally not used
because of their close proximity to the voice band which starts at 300 Hz. In addition,
tones 11 (97.4 Hz), 39 (69.3 Hz), 40 (206.5 Hz), 41 229.1 Hz), and 42 (254.1 Hz) are
normally not used because they may cause interference with adjacent tones.
A reverse burst is transmitted when the push-to-talk switch is released and also detected
when calls are received. It is a 180-degree phase reversal for a period of time determined
by the tone frequency, and it eliminates the squelch tail (noise burst) in the receiving radio.
Both the transmitting and receiving radio must be equipped with this feature for it to be
utilized.
when calls are received. It is a 180-degree phase reversal for a period of time determined
by the tone frequency, and it eliminates the squelch tail (noise burst) in the receiving radio.
Both the transmitting and receiving radio must be equipped with this feature for it to be
utilized.
5.4.3 Digital Call Guard Squelch
Digital Call Guard squelch (DCS) uses digital data instead of subaudible tones to control
the squelch. This data consists of continuous repetitions of 23-bit words. No bit or word
synchronization information is used. When the push-to-talk switch is released, a turn-off
code is transmitted which eliminates the squelch tail similar to the reverse burst.
the squelch. This data consists of continuous repetitions of 23-bit words. No bit or word
synchronization information is used. When the push-to-talk switch is released, a turn-off
code is transmitted which eliminates the squelch tail similar to the reverse burst.
Although there are thousands of possible code combinations with 23 bits, only 83 are
unique with the data scheme used. The number specified when the code is programmed is
actually a seed for a special algorithm used to generate the 23-bit data word. The data is
transmitted at a rate of 134.4 bits per second. Therefore, approximately six words are
transmitted each second. When the data is decoded, 23-bit samples are taken and then the
bits are rotated to determine if a valid code was received.
unique with the data scheme used. The number specified when the code is programmed is
actually a seed for a special algorithm used to generate the 23-bit data word. The data is
transmitted at a rate of 134.4 bits per second. Therefore, approximately six words are
transmitted each second. When the data is decoded, 23-bit samples are taken and then the
bits are rotated to determine if a valid code was received.
5.4.4 Selective Squelch Code Select (CTCSS/DSC/NAC)
Note
Call Guard codes may be permanently reprogrammed by keypad programming (see
Section 5.16).
Section 5.16).
This feature allows the normal transmit and receive Call Guard (CTCSS/DCS/NAC)
programming to be temporarily overridden with a code selected from a preprogrammed
list. It is available if the SQ LIST option switch and a CTCSS/NAC code list have been
programmed.
programming to be temporarily overridden with a code selected from a preprogrammed
list. It is available if the SQ LIST option switch and a CTCSS/NAC code list have been
programmed.