ISC D4 Work/Rescue Descender
The D4 from ISC is a heavy duty descender belay device designed specifically for arborist and industrial use. It uses a camming action that holds/stops the users weight on the rope. Actuating the lever allows controlled lowering and descent and the built in anti-panic safety prevents uncontrolled or over-speed descent. The anti-panic feature was designed with input from professional users and allows precise controlled descent without some of the side-effects seen in similar devices.