It is used for triggering a camera remotely to reduce camera shake, especially during long exposures on a tripod.
Technology: Features a locking mechanism (often called a "B" or bulb lock) that allows the shutter to be held open for long periods without continuously pressing the button.
Design: Consists of a sturdy steel cord enclosed in a flexible black vinyl casing, with a threaded tip designed to screw into standard mechanical camera shutter sockets.
Function: When the plunger at the top is pressed, it pushes a small pin at the other end to trigger the camera shutter mechanism.