The ON/OFF key is a toggling secondary power switch. Part of the instrument is always ON as long as power is applied, and this standby condition is indicated by a red LED above the key. This indicator is consequently not lit while the instrument is in operation.

CNT-91R and CNT-91R/AF only

While the rubidium oscillator is warming up, an open padlock symbol labeled RB is flash­ing at the top right corner of the display, indi­cating that the control loop is not locked. Normal time to lock is about 5 min. Do not start measuring until the unlock symbol disappears.

New Message Box

Information exchange between the rubidium oscillator and the CPU takes place over a serial bus. Any malfunction in the UART-con-trolled communication link will be reported in a pop-up message box on the display.

CNT-90(XL) w. Option 23/90

The User Interface Screens have two indica­tors near the upper right corner of the display. One is a power supply status indicator, and the other is a battery charging level indicator.

The status indicator shows:

  • a fixed battery symbol when the internal battery is the active power source
  • a charging battery symbol when the in­ternal battery is being charged
  • a power plug symbol when the mains is the active power source
  • a power plug symbol on top of a battery symbol when the instrument has been prepared for UPS operation and charging is not going on

The charging level indicator shows:

  • the relative charging level in percent