MX800 Transceiver Technical Manual
© SPECTRA ENGINEERING 2006 Revision 4.2.3
30
3.8 T08 VF Delay
3.8.1 Description
This option provides a 40mS delay to the received audio. When the option is
fitted delayed audio is fed to the line and talkthrough paths but discriminator
audio (output on CN1 Pin4) is undelayed.
This option is intended for two main applications. Firstly when the delay is
fitted, the mute (squelch) "crash" characteristically heard when a mobile
releases its PTT but the repeater tail continues, it is eliminated. Secondly
systems (including trunking systems) which have mixed voice and data on a
channel can delay the VF signal to line and air so that in the event that a data
stream is detected (by the data controller) the VF to line and air can be
disconnected for the duration of the data burst thus avoiding radio system
user annoyance. Internal switches in the MX800 may be used to disconnect
the audio under the control of the RX TALK line (CN1 Pin7) the sense of
which may be inverted using JMP12 on the micro controller.
This option may be fitted at order placement or retro fitted subsequently. The
Option PCB assembly is fitted above the Micro controller on four hex pillars.
A 16-way ribbon connection is made from the Option PCB to SKK on the
micro controller card. The links on the Option card are set as below. Once the
delay option is fitted the "Delayed Audio Option" check box is ticked in the
MXTOOLS Configuration screen (Hardware settings tab).
Note that this options PCB is also used for T09, CTCSS Suppression
Upgrade Filter and T10, the Low Standby Current Mode and all three are
independent and may be used separately or together. If the option PCB is
ordered for one particular option it may or may not be populated for the other
options.
Figure 3-7MX800 T08,T09,T10 Option board complete
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