Focus of the patent is membrane based gas dehumidifiers for waveguide units and communication systems. The fundamental concept behind dehumidifiers is absorbing moisture contents of the gas and mostly water vapor surrounding the electronic components to prevent any adverse dielectric effects in the system and especially in sensitive communication units.

A gas dehumidifier system, as described in the background section of the patent, consists of a gas compressor typically connected to the atmospheric air, a heating chamber with a heating element, a membrane cartridge (in the membrane type dehumidifiers) to absorb the moisture from the pressurized gas flowing through the membrane and a control flow valve routing the dried air to the inlet of the dry air system. The system is generally sealed and with pressurized air within the system, humid air from the outside is prevented from entering in the system. To maintain this positive inside pressure, the compressor is needed to operate intermittently and supply the positive pressure to the system. For membrane cartridge based dehumidifiers, this intermittent application of the compressor results in forcing the membrane cartridge to be inactive periodically reducing its ability to effectively absorb the water vapor from the air during cyclic or intermittent operation of the compressor. Moreover, as the flow to an inactive membrane is restored, it will take some time for the membrane to reach its optimal performance. To keep the membrane active, the dry air downstream the membrane is allowed to flow backwards toward the cartridge and stop short the compressor via a check valve (a valve that allows flow of gas or liquid in one direction only). The arrangements for such bypass system and required hardware (control valves and check valves) are presented in the patent.

Patent 5,118,327, filed by Nelson et at. in 1992, with 14 claims seems to be a continuation of Keyser's patent with an additional reference in the title to "controlled dew point" of the gas being dehumidified. This phrase appears to be implied in the earlier patent as well as the bypass system and pressure control valves used in the system essentially ensure the moisture content of the gas used for dehumidification are controlled which in technical terms translates to controlling the dew point of the gas. However, it appears that the addition of this feature was adequate resulting in issuance of another patent within 2 years of issuance of the original one (see similar patents below).

Overall, both patents have clearly stated the claims, background and details of the invention for application of their control system for membrane based gas dehumidifiers.