Panasonic KX-TD500 - Manual (Page 183)

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Programming Guide 183
Parameter Reverse Signal Detection
Default Enable: [NZ], Disable: Others
Value Range 1. Enable
2. Disable
Description/Function If an ELCOT / RCOT card is installed in the system, reversal of CO
line polarity is monitored at each port by default. Specifies whether
to enable or disable this monitoring function.
(Assignable only when an ELCOT / RCOT card is installed in the
system.)
Reference None