Received Signal Strength Indicator

Received Signal Strength Indicator (RSSI) Generic radio receiver technology metric of the power present in a received radio signal. 

The probe is traversed automatically over the structure and the amplitude of the signal associated with transmission through the structure is indicated on an X-Y or similar recorder. The X and Y co-ordinates correspond to the position on the surface, while some other parameter is used to indicate quality. One method uses different tones to indicate the strength of the received signal (i.e. joint quality), while another uses a modification to the pen X or Y coordinate to indicate a change in the signal. 

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