A step-driven digital magnetic recorder

The design and installation of a freight-car information sorting system for the. Chicago, Rock Island and Pacific Railroad was recently completed by the Stromberg-Carlson Company. The system, located in the Chicago, Ill., offices of the Rock Island Line, receives information on train make-up from several distant marshalling yards via teletypewriter links, records these messages, and sorts them. The Wheel Report Sorting System, as it is called, sorts the incoming information according to state of origin of shipment and state of destination, and routes this information to teletypewriters assigned to these states. In the course of designing the sorting system, a requirement developed for a means of storing multiple incoming messages efficiently, while sorting units are busy. The storage means must permit simultaneous recording and read-out at different rates, and must also operate intermittently on read-out due to switching of output during sorting. This service can be provided by paper-tape punches and readers with a buffer loop between. However, the information density on paper tape is low, thus creating a need for a physically large buffer storage. This fact, coupled with the need for continuously replenishing the tape, and the maintenance requirements of punches, led to the search for a more suitable means of storage. Magnetic recording presents the possibility of higher information density in addition to using a reusable medium. However, magnetic tape recorders of the conventional capstan-drive type do not generally provide for differing speeds of simultaneous recording and read-out with a buffer loop between for “first in, first out” storage. In addition, the requirement that the read-out be intermittent due to the setting up of connections to different printers is difficult to achieve without sacrificing information density for starting and braking space.