Tyco 1 kB magnetostrictive delay line memory

One kind of "delay line" memory is the so-called magnetostrictive memory. This technique is based on the idea of the propagation of ultrasonic waves through a thin wire. The information to be stored is fed into a long wire by the effect of magnetostricion (the wire contracts when exposed to a strong magnetic field – this in turn yields an acoustic wave traveling across the wire). A bit pattern created by this effect travels along the wire to its end where the information is picked up by a piezo electric element. The output of this pickup will be amplified and fed back into the beginning of the wire loop.

This basically yields a sequential storage circuit - an impulse pattern will run in an endless loop through the wire. To insert information into the loop some (simple) additional circuitry is necessary. To delete bits, the feedback loop will be opened while setting bits requires an OR gate at the input of the wire loop.

This type of memory is volatile and has a rather long access time – on the other hand, its capacity depends mainly on the length of the wire and the basic clock of the surrounding circuitry so it may easily expanded. In addition to this it is relatively inexpensive and rugged making it suitable for applications like desktop calculators and the like.

This information has been taken from http://www.technikum29.de/en/computer/storage-media.shtm. This link has excellent internal photographs of the unit.

Our unit was kindly donated by William H.L. Williams.