Emerson Level-Trol 2500 Series Instruction Manual page 22

Type 2500
CD2114−E
BO998−1/IL
Figure 12. Direct-Acting, Right-Hand-Mounted 2500-249 Series Controller/Transmitter
closes the inlet end and opens the exhaust end of
the relay valve which allows output pressure to
exhaust. This relay valve action reduces the output
pressure to the final control element and is the
reverse of the previous explanation.
22
The proportional valve varies the reaction of the
Bourdon tube to changes in the output pressure. For
additional information on the proportional valve
action, refer to the following proportional valve
subsection.
Instruction Manual
Form 1013
December 2005