When the emergency system is switched in, cam rod 1, linked to this system, is shifted to the left from its middle position, contacting the rounded heads of plungers 2 and 3 and pushing the former downward and allowing the latter to be shifted upward by spring 4. This opens admission valve 2 and closes drain valve 3. Compressed air from the tank is admitted through connection 5, channel a and connection 6 to the brake cylinders, braking the wheels. When the brake lever is released, spring 7 returns cam rod 1 to its middle position in which both of the valves are closed, holding the brakes in the applied position. To release the brakes, cam rod 1 is shifted to the right, at which admission valve 2 remains closed and drain valve 3 is opened, connecting the brake cylinders to the atmosphere through port d (as shown).
$3628$SHP,Va$