ELECTRIC WARNING SWITCH. For operating warning light or alarm. Described and illustrated on page 3.TO SPECIFY WITH SWITCH LOCATED AS ILLUSTRATED ON PAGE 3 ••Example: for Switch with 2 psi By-Pass, Housing No "801161-0200" becomes "801161-0202". For Switch with 3 psi By-Pass, Housing No. becomes "801161-0302". TO SPECIFY WITH SWITCH LOCATED 1800 FROM THAT ILLUSTRATED ON PAGE 3 •••Example: For Switch with 2 psi By-Pass, Housing No. "801161-0200" becomes "801161-0203". For Switch with 3 psi By-Pass, Housing No. becomes "801161-0303". MARVAIR DIFFUSER. Use with pumps sensitive to cavitation caused by large air bubbles that often form in suction filters. And use with all variable displacement pumps, which promote the formation of large air bubbles because the filter is oversize at low pump flow rates until full volume output is attained. The air bubbles are broken up by the Diffuser into tiny bubbles that are quickly and harmlessly dispelled through the pump. To order a Marvair Diffuser, replace the dash (-) in the Housing Number with a "0". Example: "801161-0200" becomes "80116100200". SEALED DUST COVERS. Protective, transparent dust covers for Colorator Indicators are provided by Marvel at no extra cost. The Sealed Covers are optional (at no extra cost) on Marvelbo-S and Marvel R Filters. When Sealed Covers are supplied, the Colorator Indicator Ring (Item 14) is omitted to accommodate the Sealed Cover Installation. To specify the Sealed Cover, merely replace the dash (-) in the Housing Number with an "E". Example: "801161-0200" becomes"8011601E0200". OVERSIZE INLET PORT (One size larger than standard) is available a t nominal cost on Marvelbo-S filters in both pipe-thread and straight thread port models. To specify, change 3rd digit from left in·Group A Housing Numbers (Col. 4) to a "3". Example: "801201-0200" (pipe thread housing) becomes "803201-0200"; and "801202-0200" (straight thread housing) becomes "803202-0220". In the Group B Housing Numbers (Col. 6), to specify the oversize inlet port, change the 3rd digit to a "4". Example: "802481-0200" becomes "804481-0200" .