A control panel that is either connected via a cable or using infrared. A simple one allows the slides to be changed forwards or backwards and the focus to be controlled. More advanced ones have built-in light pointers and slide preview window.ephotozine
The ability to trip the camera shutter from a distance using a cable release or wireless transmitter / transceiver.
CCD chip is separated from camera body by cable, making overall camera size considerably smaller. For surveillance situations where space is limited.
User is off site yet can still survey site via surveillance camera feeds displayed on monitor. Data transfer from camera to user can be by Internet or Ethernet, using IP cameras.
Operates in computer presentations without requiring direct access to projector, for freedom of movement.
a device used to fire speedlights off camera. Pocket Wizard is a popular brand.