This invention relates to a monolithically integrated threshold switch which switches on at an upper voltage value of a hysteretic characteristic and switches off at a lower voltage value especially adapted to I.sup.2 L ICs. Over a resistance the value of which determines the upper voltage value the input is fed to the base of a first transistor which has no injector nor current feeding, and to a first collector of a multicollector transistor the base of which is fed to its second collector and to a current source. Any output signal may be derived from any additional collector of one of the two transistors.