input on pin 2 of operational amplifier 2 oa operational amplifier 2 oa includes an input resistor 10r with pin 2 a feedback resistor 11r from j 8 to the first input a resistor 12r from the second input on pin 3 to ground and a feedback resistor 13r from junction j 8 to the second input on pin 3 from the second end of resistor 13r two parallel branches are connected to the measuring input of the integrator amplifier 3 oa including the aforementioned diode 5d for positive current and 6d for negative current e g for the consecutive slopes of ramp signal q by changing the position of the arm of potentiometer 4p at the input of 2 oa it is possible to vary the slope of both portions of the ramp q since the amount of current charging capacitors 1c and 7c is accordingly varied therefore potentiometer 4p varies the total period of signal y positive currents flowing through diode 5d are affected by the current divider consisting of 14r and 3p negative currents flowing through diode 6d are affected by the current divider consisting of 15r 16r 17r and 3p changing the position of the arm of potentiometer 3p.