The reflection alarm unit receives a DC input representing the total output power to the antenna, and the amount of reflected power, from a measuring coupler. These values are presented on the upper line of a display on the front panel of the unit. A microprocessor calculates the reflection factor (R) and from this the standing wave ratio (SWR). Both values are presented on the lower line of the display. The standing wave ratio is also compared with two locally set voltages to obtain alarms at two levels. The alarm signals are forwarded to all connected channel units via the alarm unit. The samples from the measuring coupler and potentiometer settings are converted to digital form for the processing in an A/D converter (not shown in the diagram). The circuits are distributed on two cards, one reflection measurement card and one reflection display card.