Slow-acting relays: I. Historical aspects

Slow-acting relays have been the unobtrusive little behind-the-scenes timing-control elements in various kinds of electrical installations for so long that they now are taken for granted. Although supervisory control, telemetering, and protective relay systems for electric power systems, have been covered extensively in technical literature, the role played by the slow-acting relay for the most part has been passed over. In a like manner, much has been written about machine switching in automatic telephony, but little has been said about the slow-acting relays at the heart of the works. Aware of this deficiency in published information, the AIEE committee on communications, under direct sponsorship of the subcommittee on quick and slow-acting relays, arranged a conference at the 1946 AIEE winter convention for the purpose of preliminary exploration of the subject and of the interest in it. The essential substance of that material is presented in these articles.