ARTICLE 647. SENSITIVE ELECTRONIC EQUIPMENTARTICLE 647. SENSITIVE ELECTRONIC EQUIPMENT647.1. Scope. This article covers a new 60/120-V distribution system designed to eliminate the effects of electronic noise, originally on audio and video production when this material was a Part (G) in Art. 530, and now in a more broadly applicable format. This system, as shown in Fig. 647-1, uses two ungrounded circuit conductors at a potential of 120 V, and the system secondary is midpoint tapped and grounded to hold the system to 60 V to ground.