Abstract: A multi-stage electromagnetic interference suppression circuit is disclosed which utilizes a diverter network, an impedance network and a clamping network. The diverter network includes a series combination of a varistor and a three terminal gas arrester to suppress incoming transient energy in both normal and common propagation modes. The clamping network serves to suppress any transient energy overshoot which is not suppressed by the diverter stage. Radio frequency interference is filtered by X and Y capacitors forming LC filters with an inductance in the impedance network.

Abstract: A pressure/temperature test plug assembly is disclosed as including a cap retaining device having a chain which interconnects a closure cap for the plug with the plug body in order that the cap will not be lost when measurements are taken at the test plug. The device can be installed simultaneously with the installation of the test plug or can be retro-fit onto existing test plugs.