Most modern shortwave machines use an oscillating magnetic field to create currents in the tissues (often referred to as inductothermy).

The current from the machine is generally passed through insulators (pads, tubes, treatment heads etc.) as a displacement current. What this means is they can be used with an air gap between the machine and the patient (low and Reed 1994).

Lets start with some simple principles.

We need to make a capacitor field (a way for the field to flow)

All machines have electrodes in some shape or form to create a capacitor field. There are 2 main types:

1. Traditional 2 electrode design (one positive one negative)
2. Single electrode (a coil the current flows around)

Two electrode design:

Here we have a positive and negative electrode these can be a flexible pad (good for lying on a patient or for the patient to lye on conforms well to the shape of the body)

Flexible pad style

These are generally 2 flexible rubber pads that can be applied to the patient (normally a soft cloth pad is used in between the patient and the electrode) which then plug into the machine 

Rigid plate style

These rigid plates (normally round) are normally applied near to the patient (again if touching the patient normally a soft cloth pad will be used). They have the advantage of staying in place where a soft pad would fold. Good for limbs/hips/shoulders when the patient is sat.

When using a basic form of electrode you will need 2 (one is the +ve and one the -ve).

A basic treatment set up would look something like this:

Contraplanar using 2 rigid electrodes (you can apply contraplanar at any angle through the body e.g. left to right or front to back etc.)

You can also mix the pads i.e. a plate one side and a pad the other.

A slightly different version of this is a coplanar treatment:

Now the elctrodes are placed along the body.

Some machines offer more than 1 channel of shortwave so they are able to ‘crossfire’ this simply means you have 2 lots of shortwave with 2 positive and 2 negative hence 4 electrodes. Corss fire is normally done front to back and side to side at the same time.

Electrodes can be place unevely in relation to the part. This will lead to more energy under the electrode closer to the body:

The same effect can be attained using different sized electrodes. With more energy towards the smaller electrode.