Re: Tek 2235 with long persistence orange screen and unknown opt 76


Before digital storage, CRTs with P7 (or other long-persistence phosphor)
were used for physiological monitoring. The early patient monitors in ICUs
and ORs had these CRTs. The reason was that with the long persistence, the
trace would be visible on the screen for several seconds - usually long
enough for the trace to cross the screen. Sweep speed was usually in the
neighborhood of 25mm/sec. Nurses and physicians could see the trend in some
signal like an EKG or pulse oximeter over the past few seconds rather than
just the single waveform or two.

HP/Sanborn made a lot of these systems. Tektronix made monitors for these
systems but I don’t know if HP/Sanborn used them.

I had a Heathkit scope called an “IMPScope” - Instrumentation Methods for
Physiological Studies. It had a P7 phosphor tube in it. It also had an
electrical stimulator for nerve or muscle studies.

Digital storage changed all this.

Steve Horii

On Tue, Jan 26, 2021 at 10:35 Harvey White <> wrote:



On 1/26/2021 4:47 AM, Jean-Paul wrote:
Bonjour a Tous:

In 1961-3 I had found 3" P7 round CRTs at Radio Row in NYC with the 17
pin (diheptal?) sockets, ex WWII radar tubes.

I built a tube (valve) scope from scratch based on a Heath kit.

The P7 was used to observe transients in exploding wires, for a science

Not bad for a teenager...


Join to automatically receive all group messages.