syntonizer

from The Century Dictionary.

• noun A device for the electric tuning or adjustment to resonance of circuits used in producing and receiving electric oscillations. See syntonism and syntonic.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Physics) One that syntonizes; specif., a device consisting essentially of a variable inductance coil and condenser with a pair of adjustable spark balls, for attuning the time periods of antennæ in wireless telegraphy (called also syntonizing coil).