This same technique can also be used for gap-fill exercises. Write a text or sentences with missing words on one OHT and write the missing words on the second. In the class you display the first OHT and when ready for the answers you overlay the second. If they are lined up cor rectly, as described above, the answers will sit clearly in the gaps. 2. The reveal This technique involves covering part of the OHP with a plain sheet of paper. Because paper is not transparent, any text on an OHT under the paper cannot be seen. Instead of using an overlay to show the answers to questions, you can have all the information on one OHT. Line up the piece of paper so it is covering everything except the first question and answer. When you are ready to go on, move the piece of paper down to reveal the next question. Using this technique means that the students aren’t looking at all the questions at the same time. You can focus only on the question you want to.
The OHP is a very useful classroom aid but there are a number of practical considerations to think about when using one.
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Too much information!
Although the OHP is a very clear and convenient way of displaying information, try not to use it as the basis of a classroom lecture. If everything is shown on your OHT the students might get bored because all the information is there and they won’t need to listen to you. So, either use it with the blackout technique and just reveal each point as you’ve talked about it, or put it up at the end of your lesson as a reminder and a summary.
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Placement and focussing
For the projected image to be clear and easy to read, the OHP has to positioned carefully and focussed manually. It’s best to set this up, if possible, before the start of the class.
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Bulb
Many OHP’s have a spare bulb inside the body of the projector. It is not uncommon for OHP bulbs to ‘blow’. If this happens in the class all is not lost if you know how to find and change the old bulb for the replacement one.
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Pens
There are many different coloured pens available for use on OHTs. They come in different thicknesses. Be careful though as some pens are ‘permanent’ - this means that once you write on an OHT you cannot erase what you have written. If you want to be able to clean and reuse OHTs be sure to use a temporary marker.
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Copying on to OHTs
It is possible to obtain OHTs which you can use in a photocopier. However, normal OHTs will cause great damage to a photocopier. If you want to photocopy on to an OHT, make sure you have the right kind!
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Light
As the image from an OHP is projected light, it is often necessary to darken the room so that the information can be seen clearly. When using an OHP be prepared to turn off some or all of the lights and close curtains and blinds.
Tape recorders The tape recorder is perhaps the most common piece of technology that teachers have access to. Most course books have listening activities and the course cassette is an invaluable resource for the teacher.
