Bailey 820 Line of controller cards, TT-20 H/A Transfer Station.
The Bailey Controls TT-20 (often referenced as TT20) is a vintage Hand/Auto (H/A) Transfer Station designed for the Bailey Analog Control System and Network 90/INFI 90 architectures. It provides operators with manual override andbumpless transfer capabilities between manual and automatic control of field devices.
Core Features & Functions
- Mode Selection: Allows operators to safely switch a control loop between automatic (computer/controller-directed) and manual (operator-directed) modes.
- Manual Override: Features pushbuttons and knobs that allow direct control over final output actuators (such as pneumatic devices or valves).
- Bump-less Transfer: Incorporates internal relays and circuits designed to prevent sudden process spikes or bumps when switching between hand and auto modes.
- Indicators: Works in conjunction with other analog system components to provide readouts of the measured variable, set point, and valve/actuator position.