The 1CP1 is a one inch oscilloscope tube. They were made in large numbers from the early 1950s and were used for transmitter monitors as well as miniature oscilloscopes. This tube is of Mullard or Philips construction but is unmarked. The 1CP1 was made by several manufactures including Cossor, Emitron and Pinnacle. Although delivering the same final specification each make used a different internal construction.
The final anode voltage of 1,000 is the maximum and good results can be achieved with 650 volts. This can be achieved with a simple voltage doubler from the main HT transformer winding. With much lower a3 voltages the image becomes dim. The sensitivity of the electrostatic deflection is a function of the final anode voltage. For Y sensitivity the formula is 95/a3 mm/Volt. The X formula is 110/a3 mm/Volt.
See the above advert for a typical circuit.
The electron gun and electrostatic focus can be seen. Just before the graphite coating, that obscures the deflection plates one can see the small metal springs that hold the gun firmly in place within the tubular envelope.
The phosphor covers the end of the envelope. The screen is not completely flat and is slightly domed for strength.
The pressed glass foot is covered by the plated base, and the central locating spigot covers the evacuation seal.
The end window is 26.6 mm in diameter and excluding the base pins is 85.0 mm tall.
References: Data-sheet & Etel Advert. Type 1CP1 was first introduced in 1953. See also1953 adverts.