The Valcom VMT-1 transformer is designed to match inputs from or outputs to a 600-ohm line.
Used as an input-matching transformer, it connects telephone systems to most public address amplifiers, for telephone paging. In addition it functions as an output-matching transformer to feed program material over a 600-ohm telephone line for "music-on-hold". It is compatible with any amplifier having a 25V output connection.
The VMT-2 is an audio isolation transformer. It may be used for magnetically coupling line level audio. Common uses include isolating ground references from one audio circuit to another.