All ignitors manufactured by Schiederwerk work on the principle of superposition.
To start a high pressure discharge lamp, a specified ignition voltage must be fed to ionize the discharge path at the lamp. The value of the required ignition voltage depends on the used lamp type.
Generally sodium vapor high pressure lamps (HS) and metal halid lamps (HI) need considerably higher ignition voltages which overlap the lamp's no-load voltage.
Besides, distinction is being made between ignitors that can ignite cold lamps only (ignition voltage ca. 4kV) and ignitors that allow for ignition in all operating conditions.
The permissible ignition voltage for hot restrike ignitors is limited by the lamp design and by the socket.