tickler coil(n = noun.artifact) - a small coil in series with the anode of a vacuum tube and coupled to the grid to provide feedback;
is a kind of coil

choke coil, choking coil, coil, coil spring, field coil, ignition coil, inductance coil, induction coil, primary coil, reactance coil, rotor coil, ruhmkorff's coil, secondary coil, spark coil, stator coil, tesla coil, tickler, tickler file