GAI-Tronics MRTI 2000 (No. PL1877A) Microprocessor Radio Telephone Interconnect Installation & Service Manual - Manual (Page 91)

PL1877A Microprocessor Radio Telephone Interconnect Parameter Modification
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Carrier Detect Methods
The following parameters determine the source of the signal used to indicate mobile carrier detect. One
of three signals can be selected. These are as follows: external logic level input, internal squelch, or
internal VOX. The active polarity of the external input can also be selected. By default, the PL1877A is
configured for internal squelch carrier detect.
Parameter Function
3 0 = Internal carrier detect
1 = External logic level carrier detect
4 0 = Carrier detect input is active low
1 = Carrier detect input is high
5 0 = Internal squelch for carrier detect
1 = RX audio VOX for carrier detect
External Logic Input
Set parameter 3 = 1
Set parameter 4 as needed.
Internal Squelch Circuit
Set parameter 3 = 0
Set parameter 5 = 0
RX Audio VOX
Set parameter 3 = 0
Set parameter 5 = 1
PL Validation of Carrier Signal
When parameter 06 is enabled, the Private Line detect input is checked to determine if a valid system
carrier is present. The active polarity of this input is set by the next parameter.
6 No PL detect input required to validate carrier detect = 0
PL detect input required to validate carrier detect = 1
Default = 0
7 PL detect input is active low = 0
PL detect input is active high = 1
Default = 0