8163A/B, 8164A/B, 8166A/B User’s Guide 39Getting Started 1User Interface FeaturesIntroducing SoftkeysA softkey is a key whose function changes depending on the keys that youhave pressed before. The function of the softkey is shown on the display tothe left of the softkey.Introducing HardkeysA hardkey is a key that always has the same function.Special Module StatesBesides parameter or measurement values, you may also see some textsinstead.• - The slot is empty.• - The installed module is not supported by the firmwarerevision.Slot and Channel NumbersEach module is identified by a slot number and a channel number.You can use slot and channel numbers:• to identify each channel in the overview screen with a number at theside of the screen,• to identify each channel in the Details screen with a tab at the top ofthe screen,• to identify the channel when referencing the power measured byanother channel, see How to Reference Another Power MeasurementChannel on page -104,• to identify the channel when using an application, see Applications onpage -247, and• to identify a channel when using a GPIB command, see the 8163A/BLightwave Multimeter, 8164A/B Lightwave Measurement System, &8166A/B Lightwave Multichannel System Programming Guide for moreinformation on GPIB commands.The slot number represents the module’s position in the mainframe.Front-loadable modules are numbered:• from one to two from left to right for the 8163A/B,• from one to four from left to right for the 8164A/B, and• from one to seventeen from left to right for the 8166A/B.These numbers are displayed on the front panel beside each module slot.The 8164A/B slot for back-loadable modules is numbered zero.
