# Directional Coupler
The directional coupler decouples a part of the TX signal. This way we can observe the TX signal on the oscilloscope.

| <img src="../../_static/tutorials/2_directional_coupler.jpg" width=70%> |
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| Figure: Picture of the Directional Coupler.|

The directional coupler is used to observe the TX signal on the oscilloscope. The `FWD` port of the directional coupler is usually connected to the oscilloscope. You need to add a splitter to the oscilloscope Channel and terminate it with a 50 Ohm terminator.

The `IN` port is usually connected to the output of the RFPA.

The `Probe` port is usually connected to the `TX`port of the Transcoupler.