The electrically oxidised eureka wire is wound on perfectly round 43mm dia porcelain pipe according to length required. The vulcanite/Aluminium hexagonal/round supports light the pipe on each side with a rod and nuts. The guide rod carrying the contact block is lightened with screws to the projection of the supports and carry the third terminal which permits the instrument to be used in any step. The contact block carries smooth phosphor bronze brush contacts. The instrument is perfectly insulated. < /tr>

	Max Current	Max Resistance	Tube Dia	Tube Length
a)	6.5	4.4	43mm	200mm
b)	5.0	11	43mm	200mm
c)	4.2	12	43mm	200mm
d)	3.3< /td>	16	43mm	200mm
e)	3.3	27	43mm	300mm
f)	2.3	56	43mm	300mm
g)	1.6	50	43mm	300mm
h)	1.6	100	43mm	250mm
i)	0.8	160	43mm	150mm
j)	0.8	240	43mm	200mm
k)	0.3	1700	43mm	200mm
l)	0.3	2850	43mm	300mm
m)< /td>	8.2	2	56mm	150mm
n)	8.2	4.5	56mm	250mm