This object sets the impedance mode for an input PPS port, and is only a read indication rather than configurable when the port is set to output. Admins match impedance to the connected cable and equipment to avoid signal reflections that could corrupt the timing pulse. For example, on a PPS input port fed by a 75-ohm coax timing feed, the admin sets f3PulsePerSecondPortImpedance to match, while an output-direction port on the same chassis simply reports its fixed impedance.