— photomultiplier tubes with a photocathode which gives a current of at least 10 microamperes per lumen and in which the average amplification is greater than 10 5 , and any other types of electric multiplier activated by positive ions,
— feadáin fóta-iolraitheoirí le fótacatóid a thugann sruth 10 mhicri-aimpéar ar a laghad an lúman agus inar mó ná 10 5 an meánaimpliú, agus iolraitheoir leictreach d'aon chineál eile a ghníomhachtaítear le hiain dhearfacha,