The GN-1 nixie tube is an early example made by STC of England. Because it is among the first nixie tubes, it does not have mercury added, so it is a short life tube. Another indication of the age of this design is that the digits are made from formed wire, rather than being stamped out of a sheet. You can also see from the photographs that it came in at least two variants – one had a dark anode, the other a light anode.

The Lorenz datasheet indicates that there are two anodes; one for DC use and one for AC use. The datasheet is at the end, and I have included an English translation

Digit size	25.5mm
Min current	2.5mA
Max current	5mA
Base	B12A

The (Lorenz) datasheet

GN-1 Datasheet

English translation of datasheet

1. Operating Values (notes 1 & 2)

a) For DC voltage

Anode voltage	Ua	200	250	300	V
Anode resistance	Ra	18	33	47	kΩ
Cathode current	Ik	3.5	3.5	3.5	mA

b) For half-wave alternating voltage

Anode voltage	Ua	200	240	300	V
Anode resistance	Ra	8.2	10	22	kΩ
Cathode current	Ik	3	3	3	mA

c) For alternating voltage

Anode voltage	Ua	220	240	300	V
Anode resistance	Ra	27	33	56	kΩ
Cathode current	Ik	3	3	3	mA

Note 1)

The tube must not be operated without anode resistance. also for uniform illumination of the numbers in the cathode 1, turn on a resistor of approx. 80% of the anode resistance.

Note 2)

In AC operation, the DC anode a= is over 220kΩ to connect with the AC anode a~.

2. Limits

Minimum supply voltage	UBmin	200	V
Maximum anode current	Iamax	5	mA
Minimum anode current	lamin	2.5	mA
Minimum erase voltage	Uemin	120	V

3. Special instructions

As a supply voltage, the highest voltage available in the device with a suitably sized anode resistance should be used to minimize the differences in the current and thus in the brightness due to scattering and lifetime of the tube.

The circuit should be designed so that the non-operated cathodes are either turned off or put to a potential that they can not act as anodes against the operated cathode.