A device capable of and method for communicating auxiliary data over an alarm network tandem line, whereby noise signals are filtered. The noise signals have an amplitude less than a first threshold. Further, a tandem signal is transmitted or received via a tandem port, wherein the signal transmitted or received is substantially synchronous with a noise signal peak or the transmission does not contain a period greater than the first duration. The period is measured as between two of: one or more disruption point, packet beginning, and packet finish, adjacently disposed. The disruption point is a point where the tandem signal is below a first amplitude threshold. Further, the combined amplitude of the tandem signal and the noise signal is greater than the first threshold.