(Askeri) OPTİK NİŞAN TERTİBATI: Kolimatör, dürbün, teleskop, periskop vesaire gibi, optik bir unsuru ihtiva eden nişan alet ve malzemesi. Ayrıca bakınız: "sight"
A transparent tube or window through which the level of liquid in a reservoir or supply line can be checked visually
A clear glass device used on gas pumps, beginning in the 1940's, through which gasoline flowed, allowing customers to view the product being pumped into their vehicles, so as to give visual verification of the quality and quantity of the purchased product
The section of clear pipe which can be plastic or glass that allows the operative to observe the pool water being run to waste during the backwash process When the water appears to become clear it indicates to the operator that the collected dirt on the filter bed is removed
A window in the liquid line or in top of drier used to observe the liquid refrigerant flow