From the User Manual:
Use the front panel KEYER SPEED control to adjust speed. The exact speed and weighting can be displayed and set precisely by pressing the (ST) button and then the CW mode button. The small displays now indicate keyer speed on top and weighting on the bottom. The weighting is shown relative to 3:1 dot/dash ratio. This ratio can be adjusted by plus or minus 30 percent using the up and down arrow buttons. The keyer mode can be set to either CURTIS type A or B using the "I code" menu settings. See the section on the user menus for details on setting this parameter. In mode A, the dot or dash being sent when the paddles are released is completed and nothing else will follow. In mode B, the keyer completes the element being sent as the paddles are released and then sends one of the opposite element.