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The Ferreed

01 January 1964

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The concept of the ferreed was presented in an earlier article in this journal.1 The purpose of this paper is to describe the evolution of this device during its further development. To recollect, a ferreed is a device born of marriage between miniature sealed reed contacts (see Ref. 2) and an external magnetic circuit containing remanently magnetizable members. Operation or release of the sealed contacts can be controlled by setting the remanent members in one of two magnetic states by means of short current pulses. Among the several useful properties that can be brought about in the ferreeds by selection of the proper magnetic configurations and coil design is the ability to respond to coordinate excitation -- a vital requirement for any device considered for a network crosspoint. Recognition of the potential advantages of a switching network crosspoint with metallic contacts, absence of holding power and the ability to operate in times much shorter than prior electromechanical devices 1