This is usually found on a camera top plate. The index shows the exact location of the film within the camera and thus enables accurate measurements and calculations to be made. It is most useful for close-up work when you may want to measure bellows extension or extension tubes to help you work out magnification and exposure. Close-ups are difficult to focus with a non-reflex camera because the focus cannot be checked through the viewfinder. Instead the distance from the subject to the film must be measured accurately. Some cameras which do not have a film plane index have a serial number engraved on the top plate. The top of the figures often corresponds to the location of the film plane inside the camera. Read the rest of this entry »
There are two main types of shavers: fully portable (powered by batteries, either dry cell or nickel cadmium rechargeable), and mains powered which usually incorporate a variable voltage option switch (110-130 volts or 210-240 volts). Correct maintenance is essential if they are to work efficiently and have a long and useful life while simple care and cleaning will greatly improve their smooth operation and reduce the likelihood of recurrent breakdowns. Read the rest of this entry »
Many appliances usually powered by a mains electrical supply can now be obtained in cordless form. This means they are independent of the mains supply and powered by batteries housed within the unit. Greater flexibility of use has been given to a wide variety of equipment ranging from electric shavers to electric drills.
Small items, such as electric razors may be powered by ordinary dry cell batteries because their power consumption is low and operational time is relatively short. However, once dry cell batteries have run down, they need to be replaced. On larger appliances which are used for longer periods and for carrying out much more strenuous work, the need to renew batteries at short intervals would not only be expensive but extremely wasteful in terms of the materials used in their production. Many appliances now overcome this problem by using rechargeable batteries, which come in two versions. Read the rest of this entry »
