(under subclass 67) Alarms set off by a change in the pressure of a fluid, as a check in the flow of gas in a gas-main, a break in any of the hollow bars across jail, bank, or vault windows or doors, train air-brake pipes, etc. These alarms are generally fault or defect or burglar alarms as distinguished from signalling devices.
SEE OR SEARCH THIS CLASS, SUBCLASS:
55, for pneumatic-train-pipe signal arrangements.
SEE OR SEARCH CLASS
277, Seal for a Joint or Juncture, for a generic sealing means or process,
318, for a seal combined with a fluid pressure indicator, sampler, or inspection feature.
