Cap (or covered table) is an induction coil. It can be stabilized to form a period 3 oscillator; see candelabra for a slight variation on this.
Unattended, this evolves into an interchange.
Generation 3 of cap's evolution
Generation 22 of cap's evolution
Stabilized cap oscillator (click above to open LifeViewer
In other rules
In tlife, cap is period 4 oscillator. However, it will still act as an induction coil in the same way it does in vanilla Life.