1. A burner control apparatus for controlling fuel burner systems for firing furnace sections of steam generators in accordance with any one of a plurality of operational specifications for predetermined general system functions including, a master section, a burner section and an annunciator section each having individual sequences comprising: a plurality of sets of logical function means having inputs and outputs, responsive to selected ones of the parameters of the system for producing output control and indication signals respectively, each logical function means including one solid state control circuit card for performing each logical function in accordance with the operational specification such as fuel trip, burner ignition, shutdown, and each card fabricated to include functional logic circuits of the AND, OR, NAND, NOR, type, adapted to perform each of the various individual logic steps relating to standardized logic sequences associated with fuel burner systems, when each of said logical function means is selectively interconnected with the other ones of said logical function means in the burner system in a selected manner, such that the system provides multiple interchangeability of said logical function cards in accordance with the selected interconnections, whereby the vapor generator is capable of being controlled in accordance with standardized logic sequences and specific logic sequence requirements.