In a network where frequency synchronous lower bit rate signals are combined to form a high bit rate signal by using hierarchies of multiplexers, i. The device includes at least one chamber connected to the protective enclosure that traps and purges gas bubbles contained or dissolved in the liquid filling the protective enclosure. In the cross section of the shank, the pocket 4 has a width of 50% to 100% of the shank diameter or width, a height of 20% to 50% of the shank height, and a length of 50% to 250% of the shank diameter or height. A strainer body extends at least partially downstream of the upstream portion. A second skew correction may be implemented by employing the first drive roller and the second drive roller to align the mailpiece in the second orientation with respect to the path of travel. The method of detecting smear of a magnetic head includes measuring electrical resistance values between pads of a slider having an integrated head main body portion, or between the pads and a conductor portion that is connected to a shield of the head main body portion to thereby detect smear development.