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8A083X30 Rev.11
APX Series P25 Interface
DVRS
User’s Guide
January 2019
Page 68 of 94
Forced Analog Mode
Forced Analog Mode is a hybrid mode in which the communications between the DVRS
and the
‘DVRS Enabled’ P25 PSU are P25 digital, while the voice communications are
‘forced’ to be analog when the MSU is on a non-P25 channel / Talkgroup. Forced analog
mode is used only
when the Local PSUs are ‘DVRS Enabled’. When the MSU is on
analog conventional or 3600 Baud trunking (analog or digital)
channel the DVR ‘forces’
the ‘DVRS Enabled’ PSU to transmit analog voice. When the MSU is on a P25 channel /
Talkgroup, the DVRS and PSU operate in P25 digital mode. At all times the signaling
between the DVRS Enabled PSUs and the DVRS is digital P25. The DVRS must be on
a DVR channel programmed for ‘F.Analog’ mode as described in the
‘Repeater
Channel Setup Menu’
section.
IMPORTANT!
Generic P25 PSUs cannot operate with a DVRS in Forced Analog Mode when MSU
is on an Analog or Type II Trunking Mode.
IMPORTANT!
The PSU and DVR PL/DPLs must be programmed to be properly matched. The
DVRS Enabled PSU must be programmed for mixed receive in order to be able to
program PL on a ‘DVRS Enabled’ channel.
Leading & Trailing Tones
The DVR can be programmed to send over-the-air Leading or Trailing tones to the
LPSUs to indicate successful MSU key up / system access.
If Leading Tones are enabled, the local PSU operation involves the following:
•
User does a quick PTT of LPSU so that MSU can request channel grant
•
User releases the PTT for a moment and waits to hear the Leading tones.
•
If the Leading tones indicate successful system access (channel grant), the
LPSU user PTTs again and talks.
•
If the Leading tones indicate lack of channel grant, the LPSU user can try the call
again.
Trailing tones are sent at the end of LPSU transmission and therefore do not require
double PTT.
Both Leading and Trailing Tones are sent over-the-air (i.e. not generated in the PSU that
initiates the call) therefore all LPSUs that are within the DVR range and switch to the
DVR channel will hear the tones.