Advanced Telecoms Online Labs

You are controlling real hardware TIMS modules in a real TIMS system, and viewing the real electrical signals via a PC based scope.

All front panel toggle switches, rotary switches and Potentiometers can be changed by the user.

All signal levels can therefore be altered and investigated.

All significant points throughout the experiment can be viewed by moving the scope leads, ChA, ChB, and triggering points can also be altered to suit.

The patching of the modules in the experiment can be altered if a SWITCH module is being used, otherwise the patching remains fixed. Modules also remain fixed for each experiment.

All the knobs and switches are controllable. This image shows a typical toggle switch and Potentiometer knob control.

To adjust knobs, you can either:

1. click on the knob and drag the knob pointer to your required point
2. click on the knob, which highlights it, and then use left or right arrows on your keyboard to move by one increment at a time.
3. click on either left half or right half of knob to rotate either anti-clockwise or clockwise respectively by one increment at a time.

To adjust toggle switches, you simply click on them and they cycle through the available positions – up, middle (for a three position switch) and down.

The scope is designed to mimic a traditional scope with manual controls. The TIME and FREQ buttons activate the time domain or frequency domain displays respectively.

To select a point to view, firstly select a scope input channel by clicking on the input terminal alongside labels ChA, ChB or TRIG. This will highlight and number ALL outputs which are available for that input to connect to. Then, click on the highlighted output you wish to view. The scope lead will connect to that point. The number of points to view is fixed and determined by the experimental setup at the net*TIMS system unit. The ‘Single / XY / Acc’ switch selects between the default of single shot mode, XY mode where ChA is plotted against ChB and Accumulate mode. Accumulate mode continuously requests a new screen capture and overlays them onto the display. This is useful for viewing Eye diagrams and other subtle variations of a waveform over time. Triggering at the same point in the waveform is usually very important when using Accumulate modes in scopes.

The ‘wiring’ button changes the look of the patching of the wires, but doesn’t change the connections themselves. This can be useful to improve visibility of connections and settings.

Use the ‘ELASTICITY’ control knob to vary the position of the patching leads to suit yourself.

Triggering is very important in net*TIMS, as always in TIMS. The net*TIMS scope has full triggering features as on a normal scope.

The Rise/OFF/Fall switch is used to turn on Triggering mode. The source of the trigger signal is then selected by the ChA/Ext/ChB switch. If EXTernal trigger is selected, then the trigger comes from the signal connected to the TRIG terminal with the green patching lead. LEVEL and DELAY set the trigger level and trigger delay time.

When using FREQ mode on a channel, the x1, x2 and x4 switch zooms in on the FFT display for closer inspection. SNGL (single) and AVG(average) mode create an FFT display based on one screen capture or several.

Beware of the aliasing which arises on digital scopes…creating false signals which appear correct. Always be aware of your time base settings and check that what you see is what you expect.