E.F. Johnson Company 5100 ES, Руководство по эксплуатации

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ES Series Models II/III Portable Radio Operating Manual 5-13
Conventional Mode Features
The priority channel sampling feature ensures that when priority scanning, messages on
the priority channel are not missed while listening to a message on some other channel.
The radio can be programmed as just described so that the priority channel is a fixed
channel programmed in the current scan list, the currently selected channel, or not used.
Note
Priority channel sampling is not available when receiving analog encrypted (DES) calls,
nor when receiving unit calls. In addition, the priority channel is not scanned if the active
channel is an analog channel on the same frequency as the priority channel and is
programmed with CTCSS/DCS squelch control.
Either a single or dual priority channels can be programmed if desired. With dual priority,
a call on the second priority channel is interrupted by a call on the first priority channel but
not vice versa. When scanning and the selected channel is a single or first priority channel,
is indicated in the display. This indication is displayed regardless of whether the
priority channel is fixed or always the selected channel. When it is a second priority
channel,
is displayed.
The priority channel sampling frequency is determined by the programmed Priority
Lookback Time A (see description which follows). For example, if 2.0 seconds is
programmed, the priority channel is sampled every 2.0 seconds when listening to a
message on a non-priority channel. When not listening to a message, the priority channels
are scanned in the normal scan sequence. With dual priority, the first and second priority
channels are alternately sampled at the Lookback Time.
Priority channel sampling occurs only with conventional priority scanning. It does not
occur with radio wide scanning, when listening to any type of SMARTNET/SmartZone/
P25 trunked call, encrypted call, or when transmitting (see preceding note). A series of
“ticks” may be heard when the priority channel is sampled while listening to a message on
some other conventional channel.
The priority sampling times are programmed by the following parameters:
Lookback Time A - This time determines how often the priority channel is checked for
activity. Times of 0.25-4.00 seconds in 0.25-second steps can be programmed.
Lookback Time B - This time determines how often the priority channel is checked
once an incorrect Call Guard (CTCSS/DCS) or NAC code is detected. Since it takes
much longer to detect an incorrect Call Guard signal than a carrier, this time should be
relatively long to prevent the interruptions from making a message difficult to
understand. Times of 0.5-8.0 seconds can be programmed in 0.5-second steps.
5.10.3.1 Changing the Priority Channel
If a fixed priority channel is associated with the current scan list, it can be changed if the
Priority option button or menu parameter is programmed. With dual priority, this function
changes only the first priority channel. To change both priority channels, use the Scan List
Edit function described in Section 4.12.1.
2