Patent ID: 7178545

Claim:
A control system for a bypass duct in an air handling system, comprising: a control signal line for receiving a pneumatic control signal selectively provided by a master controller; a pneumatic damper control assembly including a damper vane mountable in the bypass duct that is movable between an open position which allows air to flow through the bypass duct and a closed position which, relative to the open position, inhibits airflow through the control bypass duct, the control position of the control damper vane being controllable via pneumatic pressure applied through a damper control line connected to the signal line; a sensor mountable to the supply duct to transmit a pneumatic supply duct control signal via a supply line based on at least one of air pressure or air velocity in the supply duct; and a pneumatic switch connected to the damper control line and thus also the signal line on one side and the supply line on the other side, that opens or closes the connection between the damper control line and the supply line based on the difference between (1) the pneumatic supply duct signal via the supply line on one side, and (2) the combination of the pneumatic control signal, the pneumatic pressure from the damper assembly and a switch biasing pressure on the other side.