Reversible DC current switches
Thyristor current switches

The structures studied above are based on a set of specifications, an essential feature of which is the unidirectionality of the DC source in terms of current. On the other hand, in the general case, its voltage reversibility can be total, in both instantaneous and average values.

For some applications (essentially speed and torque reversible DC motor supplies, operating in all four quadrants), the current source (the motor armature) must be bidirectional; the DC current it supplies must be able to flow in either direction.

There are a number of solutions to make this possible.