Sorters Before Computers

Control Systems Before Computers

Controls before computers consisted of relays, switches and wires. When memory was needed, latching relays were generally used. Sorters must keep track of quite a bit of information for every board in the system. Magnetic drum systems were used to record the board information. The magnetic drum was a non-magnetic metal cylinder with magnetic tracks mounted on it. A set of electrical coils would either erase or record a magnetic pulse onto the track. The drum was rotated by a motor synchronized to the sorter chains. At normal sorter speeds, the drum would rotate about once every 2 minutes. The magnetic pulses would move around the drum as it rotated and were read by reed relays. When the right combination of pulses closed the correct relays, a diverter was activated and the board was diverted into a bin.

Here are some photos of a magnetic drum control system:

© James S. Gibbons 1987-2015