GAI-Tronics MRTI 2000 (No. PL1877A) Microprocessor Radio Telephone Interconnect Installation & Service Manual - Manual (Page 154)

Pl1877A – Radio Installation PL1877A Microprocessor Radio Telephone Interconnect
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2. Repeater transmit turn-off delay in repeater control station installations: When the PL1877A is being
installed in a control station controlling a repeater, it is necessary to ensure that the repeater does not
stay on the air after the control station unkeys. If the PL1877A detects carrier (and PL/DPL, if
applicable) after unkeying the control station, it is erroneously seen as a mobile transmission. In
systems that require PL/DPL and retransmit (not generate), no problem is encountered with the
PL/DPL signal (such as most community repeaters) since carrier only is not seen as a system mobile.
Some repeater stations have a jumper for turn-off delay but many delay turn-off more than a second
even though the “0” position is selected. In these cases, reducing the timing capacitor to a much
smaller value produces the required results (for example, changing C11 on a MICOR repeater
TLN4662A squelch gate module from 68
µF to 4.7 µF).
3. 60-Second Mobile Inactivity Timer: In the enhanced VOX simplex mode, the land-line caller cannot
be interrupted by the mobile (until the 30-second time-out). Therefore, it is possible for the mobile
to hear the warning ticks and not be able to reset the inactivity timer because the landline party is
talking. Therefore, it is recommended that the mobile inactivity timer (parameter 122) be set to 3
minutes of mobile inactivity in enhanced VOX simplex systems.
Intercabling Diagram – Maxar 80 Control Station to PL1877A