frank45,
Welcome to the forum. These are the physical variables for ringing coming out of the Phone Port:
Physical Interfaces -> PHONE Port -> Ringer -> RingFrequency
Physical Interfaces -> PHONE Port -> Ringer -> RingVoltage
Physical Interfaces -> PHONE Port -> Ringer -> RingWaveform
They can be changed by going to the Expert Configuration Pages via OBi Dashboard. If you wish to change a value, then uncheck both boxes to the right of it, leave them unchecked, change the value, press submit button at bottom of page, wait two minutes for OBi to reboot.