These are short duration currents having pulse duration ranging from 0.1 – 1 ms.

Types of low frequency currents:

     i.        Direct current:

a)   Constant direct current:

These are unidirectional flow of electrons towards the positive pole. The therapeutic use of unidirectional flow of currents is to introduce medication into the body tissues called Iontophoresis.

b)   Interrupted direct current:

If the continuous unidirectional current is interrupted, it gives rise to series of pulses or phases of unidirectional current.

   ii.        Alternating current:

In alternating current the electrons are constantly changing the direction. Electrons in the alternating current always move from negative pole to positive pole. This is used to reduce edema and relief of pain.