The NuTone NA300TA Transformer has been discontinued. The M&S TE5D transformer is an identical substitute.
The NA300TA for intercoms is a dual-output 16-volt AC, ETL Listed, 37 VA direct wire transformer used to power the NM100 and NM200 intercom systems. The output wires on the transformer are terminated with a connector that fits the NM100 or NM200 master unit.