This parameter specifies wether the analog fxo driver should fake a battery polarity inversion on the fxo line in order to advertise reception of FSK caller-id that is being received before the first ring (britsh fsk caller-id transmission variant). When set to YES, if fsk caller-id is coming on the fxo channel before the first ring, the driver will trigger a baterry polarity inversion event on the fxo line in order to advertise caller-id reception.
Valid values are: YES or NO