In the position of spool 5 shown in Fig. a, port 1, supplied by compressed air from the main, is connected to port 2. Port 3, connected to the atmosphere, is closed off. When palm button d of pusher 6 is pressed, spool 5 is shifted to the left and it blocks port 1. Port 2 is connected to the atmosphere through port 3. Spool 5 is returned to its initial position by admitting pilot air through port 4. The principle of the valve is shown schematically in Figs. b and c.
$3692$SHP,FC$