TMS device specifications:

With regards to device specifications, the magnetic field is approximately 2 tesla on the coil surface and 0.5 telsa in the cortex. The time it takes for current to rise from zero to peak is often around 70-100 microseconds. Both a monophasic or biphasic waveform can be achieved by the device. Lastly, for rTMS when pulse trains are fired, the repetition rate lies below 1 Hz for slow TMS and above 1 Hz for rapid-rate TMS.1

Magnetic coils may have different shapes. Round coils are relatively powerful. Figure-eight-shaped coils (or butterfly coils) are more focal, producing maximal current at the intersection of the two round components. The double cone coil conforms to the shape of the head and is useful for magnetic stimulation of regions deeper in the brain.