Singer Model 106 PDV-A-10508A Pneumatically Operated Control valve is based on the Singer Model 106 PG-UL Deluge main valve.
The high capacity relay valve provides on-off position operation. The high capacity relay valve, using an independent air supply, either admits inlet pressure into the main valve operating chamber from the inlet of the main valve or releases pressure from the operating chamber. The pilot system is usually piped to discharge to drain (atmosphere).