Thermocouple is safety component, which stops gas flow to the burner when there is no flame. It works on the principle of voltage as a result heating the thermocouple.

 
Basic technical characteristics and versions of thermocouples are:

-       versions:
          *  standard - coaxial conductors (copper wire inside and
              copper pipe outside). Threaded nut for coupling
              with gas valve junction
         *  standard interrupted: one of the two poles is interrupted
             to allow series connection of other safety devices, such
             as timer or thermostat
         *  double pole: separate conductors can be provided either
             with fast-on terminals, or joined to a connector for
             connection to gas valve
         *  double pole interrupted: one of the two poles is
             interrupted to allow a series connection of other safety
             devices, such as timer or thermostat
         *  single pole: with one pole only; the other one is the
             earthing of the appliance. The terminal can be either
             a fast-on or  a threaded nut

-       connection: tab terminals 6,3 x 0,8 mm or with thread
        M 8x1, M 9x1, M 10x1mm, 11/32 ̎
 
Other options of thermocouples are:

 -       connection to burner: with thread, with clamp
 -       length of thermocouple: from 250 to 450 mm or by
         customer requirement