For a dial pulsing telephone set it is desirable to have a low voltage drop across the pulsing switch 4, and a control voltage of the pulsing switch situated between the voltages of the leads 2-1 and 2-2. These demands can be met by selecting for a switching element a bipolar transistor of such a conductive type that the emitter is connected to the subscriber line. To keep this switching transistor constantly in the saturated state irrespective of the magnitude of the line current, this transistor is driven via a current source 14 supplying a current linearly related to the line current. In order to prevent the control circuit from causing too large a voltage drop for this current source, consequently leaving too little voltage for the remaining circuits of the telephone set, this current source is designed as a voltage­current source. Driving this current source can be realised by means of a voltage linearly related to the line current. Such a voltage can easily be obtained without too large a voltage drop arising across this element.