Discussion on "Electric repeaters for railway signals"

Higgins, Sach, Varley, Langdon, E.T. Rolls, A.J.S. Adams, C.E. Spagnoletti, F. Rudall
1876 Journal of the Society of Telegraph Engineers  
doi:10.1049/jste-1.1876.0007 fatcat:j3pcfwojeveopc6rvcoesverqe