Slide projectors were quite popular a few decades ago, but are still in use today. They are simply small, portable devices that project images of photographic slides onto a screen or wall. However, some new models have small built in screens that pop up for instant and portable viewing for small groups of people.
There are various types of slide projectors such as dual slide projectors, single projectors and carousel projectors. Most projectors can be operated by remote control, have auto focus, timers and are capable of using interchangeable lenses. There are 35mm projectors and medium format models available. Projectors can hold various numbers of slides and most have carrying handles. A good projector should be quiet, fast and powerful. You can buy cases to protect and transport your projector in. Slide projectors come in various, sizes, shapes and styles. They can range in price from about $50 to several thousand.