hi heckler, thank you for the answer. Every pulse have its rate time, i need pauses of of 200-400 microseconds (picbasic pauseus) between every single pulse. But if the first train with 300 pulses start and finish after 10 seconds the second train with 500 pulses start and finish in synchrony with the first after 10 seconds too. Maybe you think at the pic with the hardware pwm but with them i think its impossible to set the number of the pulses.....