Type designations and their commercial equivalents.
(Information supplied by The Inter-Service Technical Valve Committee)
Many readers, both inside and outside the Services, who are concerned with the use of valves marked with Service names, would like to know the commercial types on which the Service types were based. The following tables give this information. The first column shows the Service names, A. being an Army type, N. a Naval type, V. an Air Force type, and CV. a common Service type. Since 1941 all valves adopted by the Services have been given CV titles, and later all the old A, N, and V, valves were brought into this system to eliminate overlapping. However, as large stocks of valves marked with the old Service Type designations still exist and numerous equipments are marked with those names, they are made the basis of the arrangement in the first column.
A warning should be given that strict equivalence between the Service type and the given commercial type must not be assumed, as the specification for the Service valve may require selection either for electrical or mechanical requirements or both.
Comment by J R Hughes, BVA Technical Secretary, Wireless World, September, 1945.
In your August issue you published an 'equivalent list' of Services and commercial valve types.
This list was prepared without the knowledge of the valve manufacturers and it is felt to be desirable to draw particularly to the attention of your readers the fact that a list of this nature must be interpreted with some care, or else it may serve only to mislead.
The commercial type which is shown against any particular Services type may well be a basically similar valve but, in many cases, the two valves will be selected from the current production to specifications which are significantly different. Thus it should not be assumed that the valves shown as equivalents will in fact give similar performances in various circuit applications. The second point which should be emphasised applies wherever two or more commercial types are shown as being equivalent to one Services type. There is a risk in such a case of the several civilian types being regarded as exact equivalents to each other.