Comparisons:
 
Repeated Items
1. Bi-Metals. Copper and Brass pipe. 
2. Put a good conductor INSIDE a copper pipe.
3. Wrap a good conductor with a coil of copper wire and insert both in a copper pipe.
The basic idea for the ether transformer.
Use the best conductor as the core and wrap it many times with a thin wire. Additional coils can be added to boost performance. Shield this conductor in a copper pipe and ground one end. Bring another coil (grounded or loaded) in to resonance with the first coil.
Tesla:  He started this mess. Resonant harmonics. Use 2 wires within a coil for boosted performance and coil efficiency.
Alexander:  Wrap wire around the original wire at a 3 to 1 ratio. = 2 transformers.
Prentice: used 500K High Voltage oscillator to start harmonics, then a single wire picks up the energy. 
Coler:  Multiple Coils were tuned to this energy. Magnets were used for the transformer core.
Britten: Wrap wire with coil and insert both in a copper pipe. = 2 conductors
Markovich:  Wrap wire with wire and insert in a copper or brass tube.  = 2 transformers + shield
Keely:  Harmonics. Bi-metals. Heavy use of precious metals.
All of these pages and graphics will be posted soon.