Telephone Buildings on West Street ( Steel City House) was the 1st automatic exchange to cover central Sheffield as Ianb say a Siemens exchange. There were other early Siemens exchanges all around the same era Broomhill on Peel Street Sharrow on Aizelwood Road Attercliffe on Titterton Street Owlerton on Bradfield Road These would have covered most of the suburbs at that time The 1st 3 are still Telephone exchanges, Bradfield Road building has been sold. I am not sure of