The sampler comprises a structure, or line (24) for propagation of electrical impulses, made up of isolated sections (18-22). The sections are connected in twos by switches (28,30) with the facility to control opening and closing of the switches. The latter are either GaAs MESFET, MOS or bipolar transistors. Control of the switches is by transmission of triggering signals along a second line (26) to which the switches are connected. A synchronous signal is sent along the second line and the switches, which are normally shut, are opened by a stepped signal.