I rescued a speaker transformer from a Drive-in. remember the speakers that hung onto the driver's window?

I thought that I might be able to use it in valve radios.
Alas it is marked

1000 3.5 which I take to mean Primary 1k ohms, Secondary 3.5 ohms.

Another marking appears to read E7_1 LINE

Research by me has failed to discover what a I k ohm primary would be used with 70 Volt line? 100 v line?

What can it be used for?

Wayne.

Probably comes from a 70 volt line system.

You can use the 3.5 ohm speaker itself in any application as long as the output impedance is suitably matched. That is, the radio's or amplifier's output transformer's secondary is rated for 3.5 to 4 ohms.

Usually, where a constant voltage system is involved (70V, 100V, etc), the transformers at the speakers are tapped in terms of wattage, so you divide the number of speakers used into the output wattage available, de-rated for some headroom, and determine the appropriate wattage taps to use.

Line transformers are a completely different animal to the normal OP transformer. I was informed by several trained technicians in our Radio Club that these are really not designed to handle DC. Albeit I have used a couple in battery sets.

I have also used one with a National SW5, which has a secondary on its PP OP transformer of 1000 ohms. It was used to match this to a low impedance permanent magnet speaker, even that a N&K (German) Shell dome speaker is normally used: Headphones are driven off of the PP driver.

Marc