What are the three typical voltages used in centrally amplified paging systems?

24V and 48V are DC control voltages associated with low-voltage signaling and Power over Ethernet systems, not AC audio distribution standards used in paging amplifiers.

Constant-voltage audio distribution systems use 25V for small or low-power residential applications, 70V (nominally 70.7V) as the North American commercial paging standard, and 100V as the internationally recognized standard used throughout Europe and other regions. These voltage levels allow multiple speaker transformers to be connected in parallel on a single amplifier output over long cable runs without significant impedance loading issues. Each standard corresponds to defined power tap values on speaker transformers, enabling flexible speaker-level adjustment across the distributed system.

90V is not a defined constant-voltage audio distribution tier, and 120V is a mains AC supply voltage rather than an audio distribution standard.

48V is a DC telecommunications voltage standard for PoE or phantom power, and neither 90V nor 120V are recognized constant-voltage audio paging distribution levels.