" Our company's telephone system is connected to a 100 watt Bogen
paging amp.
I wonder how many speakers can the system handle. The speaker transformers
have wattage ratings on the primary and a speaker impedance on the secondary
to match the load. If I have 20 speakers, do I use the 5 watt taps

If you're talking about an office environment, 1/2 to 1 1/2 watts
should be plenty of power per speaker, a shop environment might
require more and you would probably use horn speakers.

Do you remember the announcements when you were in school? Most
school systems are set up using 1/2 watt per speaker. The principal's
voice was generally pretty loud.

Lee Salter