External logic carrier detect polarity, Ctcss validation of carrier, Ctcss detect input – GAI-Tronics MRTI 2000 (No. PL1877A) Microprocessor Radio Telephone Interconnect Installation & Service Manual User Manual
Page 32: Ptt sense input, Patch inhibit input, Gpi-1 input, Rx audio 2175 hz notch

PC Programming
PL1877A Microprocessor Radio Telephone Interconnect
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External Logic Carrier Detect Polarity
If Carrier Detect Source has been set to external, this determines the polarity of the Logic Carrier Detect
Input as active low or active high.
CTCSS Validation of Carrier
Disables or Enables validation of the carrier detect by CTCSS detect input.
• Carrier squelch only systems should have this parameter disabled.
• If enabled, the CTCSS detect input polarity must also be set to match the radio.
CTCSS Detect Input
Sets the CTCSS detect input polarity as either active high or active low. This must be set to match the
polarity of the radio whenever CTCSS validation of carrier is selected.
PTT Sense Input
Allows selection of the polarity of the PTT Sense Input as either active high or active low.
Patch Inhibit Input
Determines the polarity of the patch inhibit input as either active low or active high. If the patch inhibit
is not used, leave set to active low.
GPI-1 Input
Determines the polarity of the general purpose input as either active low or active high. Valid only if the
GPI-1 input has been enabled.
RX Audio 2175 Hz Notch
Allows enabling of a 2175 Hz notch filter in the path between RX audio and phone line audio and is for
special applications only.