If you touch the pod threshold fields you will see the following pop-up
menu.
TTL sets the threshold at +1.6 volts, and ECL sets the threshold at −1.3
volts.
The User option lets you set the threshold to a specific voltage between
−9.9 V and +9.9 V. If you select this option you will see a numeric entry
keypad pop-up menu as shown.
Figure 5-11. Pod Threshold Pop-up Menu
Figure 5-12. Numeric Entry Keypad Pop-up Menu
HP 16510B Menus
Front-Panel Reference 5-13