Electone "Tango 3P"... general questions

My new BTE aids have a “Telecoil” push-switch. When I push it, the aid beep-beeps, and stops ( I assume the mike is simply turned OFF). Push it again, it beeps once and returns to normal operation.
The manual says… it toggles between Mike, Telecoil, and mixed-mode(MT) ???
Does it have a telephone-coil ? How do I test it ?
( it does nothing when using my cell phone, or wireless home phones )

Is the battery in use ? Can I use it like a power on/off switch ?

Try it on a regular landline phone. If it’s telecoil, you should be able to hear a dial tone. I believe mixed mode would be telecoil with the mics on as well. I had that program on my old aids and found it useful on occasion.