[MrFixr55]

There are several speakers, including one labeled H-20 for "Central Contact" Systems. The transformers on these speakers are not designed to connect between a tube plate and B+. I am not sure, but these central contact systems may be public address systems, such as may be installed in a school, office or factory, where each classroom or room has a speaker. In this type of system, the output of the amplifier has a transformer that matches the tube or tubes to a "70V Line". These speakers may then all be connected to the 70V line in parallel. Even though the output stage of the amp has a transformer, each speaker will also have a transformer with taps to adjust the wattage that the speaker will draw. The total selected wattage should be less than the rated output of the output stage. Even in sold state PA systems, this 70V line distribution scheme is popular. In some systems like for a school, the system may have an intercom or "talkback" function, where the person operating the central system in the main office can select one speaker, address that room and then place the system into "listen" mode so the occupant of the room, such as the teacher in a classroom can address the office. Kind of like the squawk box at your local fast food drive through. These systems were common in schools. I went to Catholic school from grades 1 through 11, and it was not uncommon that when the class cut up (usually with a new teacher or a substitute teacher), the principal (usually a nun or brother) would come running with the "board of education" (a paddle). I don't know if Philco made or sold these systems, but I assume so. The 70V Line sound distribution is popular to this day, even though "powered speakers" (self contained speaker systems) fed by "line level" audio signals are gaining popularity in some installations.