This is a read-create setting that specifies what transformation, such as inverting or leaving unchanged, is applied to the 'A' signaling bit of the incoming ABCD pattern defined by cvcmABCDIncomingPattern. An admin configures this per-bit action when the CAS signaling convention used by the connected carrier or PBX differs from what the local module expects, requiring individual bits to be remapped. For example, if a carrier's A-bit polarity is inverted relative to the router's expectation, the admin would set the invert-A-bit action here to correct it.