out serially. Twistor was similar in concept to core memory, but replaced the circular magnets with magnetic tape to store the patterns. The tape was wrapped around one set of the wires, the equivalent of the X line, in such a way that it formed a 45-degree helix. The Y wires were replaced by solenoids wrapping a number of twistor wires. Selection of a particular bit was the same as in core, with one X and Y line being powered, generating a field at 45 degrees. The magnetic tape was specifically selected to only allow magnetization along the length of the tape, so only a single point of the twistor would have the right direction of field to become magnetized. The original twistor system used permalloy tape wrapped around a 3 mil copper wire. For any given length of wire, the tape was wound up over only the first half. The copper wire was then bent at the point where the tape ended, and ran back alongside the portion with the tape, forming a return conductor. This meant all the connections were at one end. Several such twistor lines were laid side-by-side and then laminated into a PET film plastic sheet, with the twistors and their return wires about 1/10th of an inch apart. A typical tape might have five twistor wires and their returns, so the sheet was just over an inch wide. The solenoid was similarly constructed, consisting of a number of 0.15 inch wide copper tapes laminated into a plastic tape of the same basic dimensions as the twistor. Unlike a traditional solenoid with many turns of wire around an open core, this system was essentially nothing more than single wires in a sheet of plastic. To build the complete memory system, a sheet of the solenoid was laid out flat, say along the X direction, and then a sheet of the twistor was laid on top at right angles to it along the Y axis. The solenoid tape was then folded over, so that it wrapped the twistor sheet, producing a series of U-shaped solenoids. Now another layer of the solenoid tape is laid over the first, the twistor tape folded over so it now runs along the negative Y axis across the top of the new solenoid tape, and then the solenoid tape is folded over to form a second set of loops. This process