The universal counter HM8123 features three high sensitivity inputs and allows the measurement of signals in the frequency range between DC and 3 GHz. Due to the high frequency of the internal oscillator of 200 MHz the time resolution is 10ns. Additional control and trigger functions are available via inputs on the rear of the instrument. There are inputs for arming, gate and trigger and outputs for gate and trigger signals.
 

1. POWER (pushbutton)
   Power switch, mains input connector on rear panel
2. GATE (LED)
   The GATE LED will be on for the duration of the gate time and synchronisation time, i.e. for the duration of one complete measurement.
3. REMOTE (LED and pushbutton)
   The REMOTE LED will be on if the instrument is under control via the interface. By pushing the REMOTE button operation will be returned to manual.
4. Display (LCD)
   Display of measurement results and additional information
5. ESC (pushbutton)
   Escape pushbutton (menu)
6. ENTER (pushbutton)
   Enter pushbutton (menu)
7. SELECT (pushbutton)
   Selects a menu or part thereof.
8. pushbuttons
   These arrow pushbuttons are used to control the menu and the parameters. Rotating knob Knob for entering parameters.
9. Rotating knob
   Knob for entering parameters
10. GATE TIME (pushbutton)
    Setting of gate time.
11. LEVEL B (pushbutton)
    Setting of channel B trigger level.
12. LEVEL A (pushbutton)
    Setting of channel A trigger level.
13. 1 : 10 pushbutton
    Input attenuator, total attenuation 100 times.
14. DC (pushbutton)
    Selects the coupling of the corresponding channel.
    Button DC lit = DC coupling
    Button DC dark = AC coupling
15. lope (pushbutton)
    This pushbutton selects the trigger slope. A lighted pushbut- ton indicates triggering on the negative slope, an unlighted pushbutton indicates triggering on the positive slope.
16. 1 : 10 pushbutton
    Input attenuator, total attenuation 100 times.