The compressor has to run with the same speed (or fixed gear ratio) as its driving turbine and have equal power and pass the same flow as its driving turbine. This constitutes a gas generator which produces gas power. The compressor also has to pass the same flow as whatever uses the gas power, ie additional turbine stages for a single shaft engine or separate power turbines or a jet nozzle. This equal-flow requirement is alongside an equal pressure-ratio requirement, between overall compression and expansion ratios, and together they position the running line for steady state operation.