ard at p850ug1.demon.co.uk (Tony Duell) writes: > I would say relays were definitely available in 1900. Yes, they were -- my 1871 copy of Robert M. Ferguson's "Electricity" describes them in the selection about telegraphic applications: http://offog.org/stuff/ferguson-relay.jpeg -- Adam Sampson <ats at offog.org> <http://offog.org/>