All of the above, which are referred to in the briefest terms only, demanded that all switching movements should be made through the medium of power-operated interlocking plants. These plants in the subway portions of the line are in all cases electro-pneumatic, while in the elevated portions of the line mechanical interlocking has been, in some cases, provided. A list of the separate plants installed will be interesting, and is given below: Location. Interlocking Working Machines. Levers. MAIN LINE. City Hall, 3 32 Spring Street, 2 10 14th Street, 2 16 18th Street, 1 4 42d Street, 2 15 72d Street 2 15 96th Street 2 19 WEST SIDE BRANCH. 100th Street, 1 6 103d Street, 1 6 110th Street, 2 12 116th Street, 2 12 Manhattan Viaduct, 1 12 137th Street, 2 17 145th Street, 2 19 Dyckman Street, 1 12 216th Street, 1 14 EAST SIDE BRANCH. 135th Street, 2 6 Lenox Junction, 1 7 145th Street, 1 9 Lenox Avenue Yard, 1 35 Third and Westchester Avenue Junction, 1 13 St. Anna Avenue, 1 24 Freeman Street, 1 12 176th Street, 2 66 ---- ---- Total, 37 393 The total number of signals, both block and interlocking, is as follows: Home signals, 354 Dwarf signals, 150 Distant signals, 187 ---- Total, 691 Total number of switches, 224