a predetermined temperature which leads to a displacement of the u shaped member 18 due to attachment 17 of expansion member 16 the right hand movable contact 21 is raised so that now the right hand connection of control heating system 38 is at a different voltage to the left hand connection thereof thus control heating system 38 is heated bimetallic strip 29 is deformed and the left hand switch opens at a second temperature fig3 shows an arrangement similar to that of fig2 the difference compared with the embodiment of fig2 is that the fixed contact 25 of the left hand half of snap action switch 41 is connected to the control heating system 43 whose other end leads to connection 37 of hotplate 11 the right hand fixed contact 40 of double snap action switch 41 leads directly to the second connection 34 of hotplate 11 while the first connection 33 of hotplate 11 is connected to input terminal 32 the operation of the arrangement of fig3 is such that when the hotplate is cold current passes through the parallel connection of the two cooking heating systems 12 and 13 following heating of the hotplate and or control heating system 43 at a first temperature current only flows through cooking heating system 12 while on a further increase thereof the left hand part of double snap action switch 41 opens and consequently interrupts the current flow through cooking heating system 12 the invention provides the possibility in all three cases of.