TOPIC 2—TYPES OF COMPUTER CONTROLLING UNITS AND THEIR CONTROLS

Toggle Switches Toggle switches work in several different ways. Let’s examine the three most common types— alternate-action; momentary-action/contact, two-position; and three-position. Alternate-action toggle switches —Alternate- action toggle switches can be permanent up and return to neutral, or they can be permanent up or down. Placing the switch in a permanent up position will turn a unit on or off, activate a function, or set a parameter. Returning the switch to the center position (neutral) may or may not interact with the computer’s software. Placing the switch in permanent up or down position can also cause an immediate or delayed response from the computer’s software. Momentary-action/contact, two-position toggle switches —Momentary-action/contact, two-position toggle switches are usually used to initiate an operation or perform a function. Depressing the switch down momentarily activates this switch, and it will then return to a neutral position (center) when not being used. Three-position toggle switches —Three-position toggle switches operate basically the same way as the momentary action/contact, two-position toggle switches except one more variable has been added. These switches can be placed in a locked up position, left in the center position (neutral), or in the down position, which can be a momentary-action or locked down position. The center position may be used to set a parameter, or it may be used to disable the locked up/down position. Two-Position Switches Two-position switches can be left in an up or down locked position. In either position there will an immediate response. TOPIC 2—TYPES OF COMPUTER CONTROLLING UNITS AND THEIR CONTROLS We have discussed the types of controls that are associated with controlling units. Next you’ll study the different types of controlling units associated with computers. It is important to note that not all types of controlling units are used to control every computer. You will not find each and every one of these controlling units on every computer you operate and maintain. However, some computers have a combination of two or more of these controlling units to enable you to operate and perform maintenance on the computer. To show you how controls and indicators are generally labeled on drawings, we selected several examples and have presented them in figures. These examples point out many of the controls and indicators used on controlling units. Learn the capabilities and limitations of each of these controlling units to enhance your abilities to operate and maintain any type of computer. We do not go into a detailed discussion of these controlling units, but rather we discuss the tasks they are capable of performing. You will find the operation of the controlling units in the computer’s technical or owner’s manual. In the operation or initial setup section of the technical or owner’s manual, you will find a general description of the controlling unit or units on your system. It will give the operation, an illustration, and tables and figures to describe each control and indicator used by the computer or associated equipment. Manuals that have a functional description section provide all details of operation. Controlling units are also supported by circuit diagrams (prints) that contain information you can use to perform maintenance. All controls and indicators are important; be particularly aware of controls that when activated interact with computer operations. Computer operations include those operations that are executed by programs/software as well as manual operations activated when performing corrective maintenance. The programs and software include the diagnostics used to perform preventive maintenance as well as the operational programs. An example of a manual operation would be a short maintenance program you would assemble and manually load into the computer and run to check a specific function of the computer. Know and understand the controls and indicators thoroughly. They are your means of monitoring computer operations and an aid when you perform maintenance. Detailed information of every control and indicator will include the following: The name of the control or indicator Type of control or indicator Function and use of the control or indicator F i g u r e 3 - 2 i s a n e x a m p l e o f a typical controlling unit for a computer. 3-4