CMS:Completing Marker 1 (CM1)
Completing Marker 1 (CM1) is a marker in the 5XB telephone switch at Connections Museum in Seattle. It is one of two completing markers in the 5XB, and one of three markers overall in that exchange.
Completing Marker 1 (SD-25550-01) is a U&Y type, named for its extensive use of U and Y type relays. This is in contrast to Completing Marker 0, which is an newer wirespring type. It was manufactured by Western Electric. It consists of four bays of equipment, plus a route relay frame shared with the other two markers.