I'm not quite sure what you exactly require. Generally for simple systems it will be an ignition spark (10KV) lighting either gas or oil. It may be direct ignition or could involve a pilot depending on the type, size and application.
Or it may be a HESI system using Capacitor discharge??
Then of course you have flame supervision etc etc.
So need more info. Rod Nissen.
Combustion & Engineering Diagnostics
canded@iprimus.com.au