Also I believe it was exposure to telephone switching apparatus that led Claude Shannon to realize that Boolean algebra could be useful for describing and analyzing switching circuits.
A book "The Design of Switching Circuits" by some Bell Labs guys Keister, Ritchie and Washburn is something of a cookbook of relay circuits for various purposes. Then at the end of the book they introduce some of Shannon's insights for circuit analysis and design. Shannon's work applied to combinatorial circuits; later it was Huffman who worked out the application to sequential circuits.