Most ultrasound devices offer the impulse (interrupted) wavelength of UL, and for many therapists, it is the preferred mode of therapy. Until recently, the pulse duration (the time at which UM energy was delivered) was in most cases 2 ms (2 thousandths of a second) with a variable period. Some KS machines now offer variants and from time to time. However, this is of clinical significance is not yet defined. Typical pulse ratio is 1: 1 and 1: 4 although there are other possibilities (see calculation of the ratio). In 1: 1 mode, we have output power for 2ms, followed by a 2ms break. In 1: 4 mode, 2ms of output power is followed by a period of 8ms of rest.

The following diagram illustrates the different pulse ratios.

The impulse K3 effect is well documented. This mode of operation is preferable, especially when treating sharper lesions (adhesions). Some manufacturers provide information about impulse ratios, for example 1: 9; 1:20. Others in terms of percent (1: 1 = 50% 1: 4 = 20%, etc.). The time the device is on or off is a relevant factor in the dosing calculation