Nikon EL2 - Manual (Page 29)

Operation via Cable Release
The shutter-release button can also be tripped via a ca­
ble release or similar accessory for more vibration-free
operation when the camera is tripod-mounted and op­
erated at slow shutter speeds. And, as two mounting
threads are provided, virtually any type cable release can
be used. To attach an ISO-thread release (Nikon model
AR-3, etc.), screw the connector into the V-shaped
thread in the center of the button. For Nikon-thread
releases (model AR-2, etc.), screw the connector onto
the threads provided around the button. The shutter is
then tripped by depressing the release plunger.