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Glossary of terms you will come across during your Phase 2 training.

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Arbitration means negotiation. For example:

In CAN bus systems, if two nodes try to access the bus at the same instant to send a message, unless we take precautions, there will be a conflict and possible data collision, with the resultant loss of data and network down-time.

In order to avoid this, the messages from each of the nodes have unique message IDs. The message with the lower ID is deemed to have the higher priority and gets sent first. Whilst this is happening, the other node goes into listening mode, and does not attempt to transmit its message. As soon as the higher priority message has been transmitted, the bus is free and the second mode can then automatically transmit its message. Conflict and data collision have been avoided, and the arbitration process only takes about 12 microseconds.


The rotating shaft of a starting motor. Inside a motor, this shaft is free to revolve. Mounted on it is a commutator which allows us to pass electrical current to windings which are wrapped around the shaft. In the middle of the armature is a laminated soft-iron core.

Typical armatures.


Arsenic is a deadly poison and is used in doping semi-conductors to produce N-type material.

That is why it is important to be careful when handling old electronic components. They may contain traces of this arsenic.


Asbestos warning signExtremely harmful material formerly used in brake and clutch lininig material, now banned form use. You may still come across it in friction and other heat resistant materials (heat shields, insulation), so treat it with extreme caution.

As can be seen from the image below, when asbestos is viewed under a microscope, we can see that the individual particles are spear like, with sharp ends. When these particles of asbestos become airborne and are breathed in, they can embed themselves in the lungs. After a latent period of about 30 years, this can cause asbestosis, an inoperable disease which will result in death.

Asbestos fibres as viewed under a microscope


In the Baldoyle Training Centre, one of the two assistant managers, Aidan Owens, has responsibility for the CP Fitters' Section.


An astable square waveAn astable circuit is an electrical circuit that does not stay in one stable condition. If you were to monitor it with an oscilloscope, it produces a 'square wave', this is a digital waveform with sharp transitions between low (0V) and high (+Vs). Note that the durations of the low and high states may be different. The circuit is called an astable because it is not stable in any state: the output is continually changing between 'low' and 'high'.

Three possible states are:

  • Astable: Not stable in any state, output is constantly changing between on and off 
  • Monostable: Stable in one state, either on or off 
  • Bistable: Stable in either state, on or off 

During the induction phase of the course, you will be issued certain tools, Tools Issued on Repayment.

As of July 2012, the cost of these tools to you is €200. This sum varies from time to time, as the prices of the tools fluctuate.

The cost of these tools is deducted from your wages over the durantion of the course, working out at €10 to €15 per week.

If you already have some or all of these tools, no issue and no deductions will be made.

You can see the full lust of tools here


This is short for 1 atmosphere, or 101.3 kN/m2 (expressed in SI units), or 14.7 psi (expressed in Imperial Units).

One atm is atmospheric pressure, 2 atm is twice atmospheric pressure.

Don't confuse this term with bar. They both measure pressure, but they are not the same.

1 bar = 100 kN/m2 = 14.5 psi

1 atm = 101.3 kN/m2 = 14.7 psi


Pressure is defined as Force per unit Area.

In the SI, Force is measured in Newtons, and area is the product of multiplying a distance (length) by a distance (breadth), metres x metres to give us a basic area of 1 square metre (1m2).

So, the basic unit of any pressure is 1N/m2, also known as 1 Pascal, or 1Pa.

This is a very small unit of measurement for practical use, so when we discuss much larger pressures such as atmospheric pressure, we talk in terms of thousands of Newtons of force, or kN.

Standard Atmospheric pressure is 101.3 kN/m2. We know that atmospheric pressure is constantly changing, and any figure above this is deemed to be high pressure, and any figure below this is deemed to be low pressure.

Within the earth's atmosphere, we have air. Although we are not normally aware of this, air has weight. This weight of air exerts a downward force on the surface of the earth.

As we gain altitude, the column of air above us gets shorter, and so exerts less force on us.

Force, acting on an area, is, by definition, pressure. In the SI, force is measured in Newtons, and area is measured in m2. For convenience, we measure pressure in milliBars. Check out the animation and see how the atmospheric pressure drops from the normal at sea level (1013mb) to lower and lower figures as we gain altitude.

Flash video(Flash animation)

The atomic number describes the number of protons in the nucleus of an atom.

This number determines the atom's place in the periodic table. In neutral atoms, the number of electrons is equal to the number of protons.

For example, copper (Cu) has an atomic number of 29. This tells us that copper has 29 protons and 29 electrons.

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