Toggle SwitchesToggle switches work in several different ways:Let’s examine the three most common types—alternate-action; momentary-action/contract,two-position; and three-position.l Alternate-actiontoggleswitches—Alternate-action toggle switches can be permanent up and returnto neutral, or they can be permanent up or down.Placing the switch in a permanent up position will turna 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 positioncan also cause an immediate or delayed response fromthe computer’s software.l Momentary-action/contact,two-positiontoggleswitches—Momentary-action/contact, two-positiontoggle switches are usually used to initiate an operationor perform a function. Depressing the switch downmomentarily activates this switch, and it will then returnto a neutral position (center) when not being used.. Three-positiontoggleswitches —Three-positiontoggle switches operate basically the same way as themomentary action/contact, two-position toggleswitches 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 downposition, which can be a momentary-action or lockeddown position. The center position may be used to seta parameter, or it may be used to disable the lockedup/down position.Two-Position SwitchesTwo-position switches can be left in an up or downlocked position.In either position there will animmediate response.TOPIC 2—TYPES OF COMPUTERCONTROLLING UNITS AND THEIRCONTROLSWe have discussed the types of controls that areassociated with controlling units. Next you’ll study thedifferent types of controlling units associated withcomputers. It is important to note that not all types ofcontrolling units are used to control every computer.You will not find each and every one of these controllingunits on every computer you operate and maintain.However, some computers have a combination of twoor more of these controlling units to enable you tooperate and perform maintenance on the computer. Toshow you how controls and indicators are generallylabeled on drawings, we selected several examples andhave presented them in figures. These examples pointout many of the controls and indicators used oncontrolling units.Learn the capabilities and limitations of each ofthese controlling units to enhance your abilities tooperate and maintain any type of computer. We do notgo into a detailed discussion of these controlling units,but rather we discuss the tasks they are capable ofperforming.You will find the operation of thecontrolling units in the computer’s technical or owner’smanual. In the operation or initial setup section of thetechnical or owner’s manual, you will find a generaldescription of the controlling unit or units on yoursystem. It will give the operation, an illustration, andtables and figures to describe each control and indicatorused by the computer or associated equipment.Manuals that have a functional description sectionprovide all details of operation. Controlling units arealso supported by circuit diagrams (prints) that containinformation you can use to perform maintenance.All controls and indicators are important; beparticularly aware of controls that when activatedinteract with computer operations.Computeroperations include those operations that are executed byprograms/software as well as manual operationsactivated when performing corrective maintenance.The programs and software include the diagnostics usedto perform preventive maintenance as well as theoperational programs.An example of a manualoperation would be a short maintenance program youwould assemble and manually load into the computerand run to check a specific function of the computer.Know and understand the controls and indicatorsthoroughly. They are your means of monitoringcomputer operations and an aid when you performmaintenance. Detailed information of every controland indicator will include the following:l The name of the control or indicatorl Type of control or indicatorl Function and use of the control or indicatorF i g u r e 3 - 2 i s a n e x a m p l e o f atypical controlling unit for a computer.3-4
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