Any shutter make,
T- set if not a self setting shutter, trip=shutter opens; second press of trip lever should close the shutter or turn the speed dial to another setting to close the shutter. Norm is either or not just one to close.
B- set the shutter if not a self setting shutter, press trip lever=shutter opens and stays open as long as the trip lever is held in the trip position and closes instantly (shutter's fastest speed) when the trip lever is released.
Timed settings- set if not a self setting, pressing trip lever causes the shutter to open and close at the selected time. Keeping pressure on the trip lever will result in the speeds being slow or the shutter to stay open until the pressure is released from the trip lever on many makes of shutters.
Standard speed tolerance is 20% for 1/100 and slower, 30% for speeds 1/125 and faster or roughly 1/3 stop error.
Shutters not preforming to these guidelines need servicing.