Table 2. Summary of stimulation parameters and a detailed description of how they are defined.

Definitions and characteristics of stimulation parameters.

Parameter	Symbol	Unit	Description
Pulse interval	T	ms	The time interval between pulses of a sequence
Pulse frequency	f	Hz	The inverse of the pulse interval, f = 1/T, is the number of pulses per second
Phase duration	t1	ms	The duration of the leading phase
Pulse amplitude	i	mA	Current amplitude measured baseline to peak
Phase charge	qc	μC	Total charge in the phase
Pulse duration	p	ms	The sum of t1+t2+t3
Carrier frequency	fc	Hz	Frequency of a carrier waveform which is modulated by the stimulation waveform
Carrier-on-time	tc1	μs	Phase duration of carrier waveform
Carrier period	Tc	μs	Inverse of carrier frequency
Phase charge density	qd	μC/cm2	The phase charge per unit electrode area
Root mean square current	irms	mA	$i_{rms}=\sqrt{\frac{1}{T}{\displaystyle \underset{0}{\overset{T}{\int }}i{(t)}^{2}dt}}$
Electrode current density	je	mA/ cm2	je = irms/A
Electrode area (active)	A	cm2	The area of electrical contact at the skin. (assumed uniform current distribution within electrode)