Power Tappers

A tapper is a device that taps off a portion of the signal while allowing the rest of the signal to pass through with a minimum of loss.

For correct function and low SWR on the main line input and output ports the coupled tapper port must be terminated in 50 Ω. 
Power tappers are frequently used in distributed antenna systems in buildings or 
tunnels.

Tappers operate similarly to directional couplers but without the directivity (no ­isolation between output port and coupled port) and have relatively broad bandwidths.