Wire contact relay for the IBM Selective Sequence Electronic Calculator(SSEC)
This is a black and white image of a wire contact relay from 1948 against a white background. Light is coming from the direction of the camera. Written on verso side of image on bottom right corner in pencil is "IBM SSEC wire contact relay" and on verso left edge of image in pencil is "P1331". There is a small separate cut-out description label of this relay. It reads "IBM SSEC Wire Contact Relays. The wire contact relays pictured here are from the IBM SSEC (Selective Sequence-Controlled Electronic Calculator). The IBM SSEC was the first machine that could control its calculating sequence by modifying its own instructions. However, it was disputed whether or not the IBM SSEC was wholly electronic, because the machine had 13,500 vacuum tubes and 21,400 electromechanical relays.".