Before revision: Originally the gas flow computer was an electronic module that simply provided a dedicated gas flow computer function.
After revision: a mechanical (1920's technology) or later a pneumatic or hydraulic computing module(1940's technology used to the early 1990's but still available from a number of suppliers), subsequently superceded in most applications with, as the primary elements switched from transmitting the measured variables from pneumatic or hydraulic pressure signals to electric current as explosion proof (1960's technology to present)) and then intrinsic safe (1970's to present) transmitters (driven by low power transistor applications) became available,Originally the gas flow computer was an electronic module that simply provided a dedicated gas flow computer function.