It was Eckert of the ENIAC team who had suggested the use of a delay line to store the pulses of an electronic computer.
There were several ideas involved.
The pipe, or delay line, would have to cope with pulses separated by only a millionth of a second, and to transmit them unsmudged.
It was also necessary that the pulses should be stored not just for a thousandth of a second,
but indefinitely, which required recirculating them through the delay line again and again.
If this were done naively then the pulses would soon become too blurred to be distinguishable.
So electronics had to be devised to detect the existence of a (somewhat degenerated) pulse arriving at the end of the line,
and to start off a clean pulse at the beginning—the electronic equivalent of the relay used as a telegraph repeater.
This would have to be combined with the facility to accept pulses from the rest of the computer and to feed them back in as required.
It was well known that it was advantageous to use a medium other than air for the sound waves, and mercury was already being employed in radar applications.
This appropriate element, was to haunt the developments of the next few years.