The lens-to-camera attachment is very important on SLR cameras. It must be easy to fit, light-tight, and link up smoothly with the camera’s controls. There are two basic types of lens mount—screw thread and bayonet. Screw thread mounts: found on the older or less expensive SLR models. Their great advantage is standardization. All screw thread lenses fit any make of 35mm camera body made for this type of lens mount. Read the rest of this entry »
When the solenoid is energized, the plunger is pulled upward by magnetic force of the solenoid coil, and the pin travels back and forth in the upper slot of the spin cam bar. This action pulls the spin cam bar backward from the basket clutch shaft, which allows the bar to slide downward toward the clutch lining. Read the rest of this entry »
Some fluorescent fittings have no starter switch(s) for the tubes. Instead there is S transformer to provide the prewarming and the tube itself has a metal stripe running throughout its length from one lamp cap to the other. The lamp caps are earthed at the lampholders.
This assists in the starting of the electron flow and, as there is no starter to operate, the lamp strikes without the characteristic delay of the switch-start type.
A fluorescent tube has an expected life of 5000 to 7000 light hours or up to seven times that of an electric light bulb. Read the rest of this entry »
Plain and twisted candle lamps are made in 25 W, 40 W and 60 W sizes and in pearl, plain, amber and silvered colours. They are made in be (bayonet cap) and sbc (small bayonet cap) versions.
These are used for wall lights and for period pendant fittings.
These are sometimes called ’strip lights‘ and are non-fluorescent, being tungsten filament lamps. There are two versions, one type is commonly used for applications in the home, and the second type is known as architectural lamps‘. Read the rest of this entry »
The amount of light given out or produced by an electric lamp — bulb, striplight or fluorescent tube — depends on the type of lamp and its wattage. The light produced is measured in lumens and a bulb or tube of a given wattage produces an average output of so many lumens. This will continue throughout most of its life.
Equally important is the number of lumens produced for each watt consumed, so it is usual to say, when comparing types, that a bulb or tube produces so many lumens per watt. The more the lumens per watt, the higher the efficiency of the lamp. Read the rest of this entry »
A radial power circuit is the name given to a circuit supplying a number of 13 A socket-outlets and fixed appliances using one cable which is not wired in the form of a ring but terminates at the last outlet.
The permitted number of socket-outlets (and fixed appliances) depends on the current rating of the circuit which can be either 20 A, wired in 2.5 mm2 cable, or 30 A wired in 4 mm2 cable. The number of socket-outlets and fixed appliances which can be served by a 20 A radial circuit depends also on the location of the circuit and whether the outlets are confined to one room. Read the rest of this entry »
Of the two principal types of cooker control unit, the type incorporating a kettle socket-outlet is the more popular. Since, however, it is important that the kettle is not used on the cooker hob where its flex would trail over a switched-on boiling plate it is better to have the unit without a socket where it has to be fixed immediately above the cooker. Read the rest of this entry »
Table lamps, floor standards, bedside lights and other portable lights can have dimmer control using any one of three methods. One method is a dimmer socket adaptor which plugs into the standard 13 A socket-outlet. This unit has two 2-pin sockets and is especially suitable for controlling two bedside lamps in a twin-bedded or a double-bedded room. The control knob on the adaptor dims both lamps at the same light intensity; they cannot be controlled independently.
Another method uses a line-cord dimmer which is wired into the flex of the lamp. The dimmer can be a standard wall type mounted on a plastic box and placed on the arm of the chair, table, desk, or any other chosen position. Alternatively, it can be a mini-dimmer switch resembling a torpedo table lamp switch. This type is especially suitable for the individual control of bedside lamps. Read the rest of this entry »
A basic understanding of electricity is essential, even for those who do not intend to carry out any repairs or servicing of appliances. Ignorance is no protection against your own or someone else’s errors and oversights, whether with repairs, servicing or installation.
Power is supplied to an electricity substation at a very high voltage — 400,000 volts — in three-phase form. There it is converted, via a transformer, to 230 volt single-phase for distribution to our homes. In normal circumstances, current flows from the live supply of the substation’s transformer, through the electrical appliances used in the house and back via the neutral conductor (cable) to the substation transformer’s neutral pole (a closed loop). Read the rest of this entry »
Aschematic diagram of the internal workings of a pod-type thermostat. This type is used in appliances that have a variable temperature control. It consists of an oil-filled pod connected to the switch by a capillary tube. When the oil in the pod is heated or cooled, it expands or contracts in the tube and operates a diaphragm. The diaphragm acts on the switchgear thus breaking the circuit and in this instance, ‘making’ the other. The cooling oil contracts, pulling the switch the opposite way — back to its original position; the process repeats if temperatures change. Read the rest of this entry »
