Specifications

ORIGINATING A CALL
When originating a call, the portable identifies an idle
repeater channel and interrogates it with a single burst of
"busy" tone, the repeater keys its transmitter and sends a
burst of "acquisition" tone back to the portable unit. When
the interrogating portable detects the acquisition tone, it then
transmits its collect and group tones, which the repeater
regenerates for all idle portable units in the system.
The idle portables, which continually scan all channels,
will stop on the active channel if any of the programmed
collect tones are detected and wait for group tone(s).
If the correct tone sequence is detected, the portables
will alert the operator to an incoming call and open their
audio circuits. If the correct sequence is not detected, the idle
portables will resume scanning the channels. Once the port-
able is "locked" on a channel, it will remain there until the
repeater times out or the operator terminates the call.
OPERATIONAL MODES
The radio will always be in one of three operational
modes; idle, wait, or ready. The three operational modes and
the conditions that cause the radio to switch from one mode
to another are shown in Figure 6.
The radio enters the idle mode when power is turned on
and begins scanning channels for incoming calls. The wait
mode is entered when the user places a call. The radio
remains in the wait mode until a channel is acquired, or if no
channel is available. The ready or conversion mode is indi-
cated by an alert tone. A tone signalling Timing Diagram is
shown in Figure 7. Sequence Flow Charts for each opera-
tional mode are shown in Figures 8, 9 and 10.
Idle Mode (Figure 8)
When the radio is in the Idle Mode, the audio is muted
and all channels programmed for call decode are sequentially
scanned for an incoming call. An incoming call is identified
by detecting one of the collect tones programmed in the area.
Upon receipt of a collect tone, the portable looks for a short
interval for the group or individual tones, providing that their
collect tones are the same. When no valid tone is found, the
portable will resume scanning the channels for an incoming
call.
If a group (or individual decode) tone is detected the
portable then looks for busy tone for a 90 millisecond period.
If four tones are properly decoded, the portable will then look
for busy tone for 270 milliseconds.
When no valid tones are found, the portable will resume
scanning for a call with the next channel. When a busy tone
is found, the portable will enter the Ready Mode. If busy tone
is not detected, the portable remains in the Idle Mode and
continues scanning channels looking for an incoming call.
Pressing the PTT switch will cause the radio to enter the Wait
Mode.
Wait Mode (Figure 9 on page 20)
When the user enters the Wait mode, the group tone is
checked to make sure it is a valid call-originate group. It if
it not valid, a high-frequency steady tone is heard in
GE_MARC V•E systems only. If valid, the radio will scan
the call-originate frequencies for brief intervals until it finds
one with no busy tone on it. If no channel is free, the radio
will activate the Call Retry state if programmed for this
option. This causes the radio to revert to the Idle mode and
scan for a call while trying the Wait mode approximately
every 20 seconds for a five minute period. If the Retry option
is not programmed the portable will sound a low-frequency
tone, and then return to the idle mode.
Figure 6 - Operational Modes
LBI-38836B
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