RST

The RST code is used by Radio Amateurs to exchange signal reports.

The "R" stands for "Readability" and is measured on a scale of 1, (barely readable) to 5 (Perfectly readable).

The "S" stands for "Strength" and is measured on a scale of 1, (very weak signal) to 9 (very strong signal).

The "T" stands for "Tone" and is measured on a scale of 1, (very poor tone) to 9 (perfect tone). Tone is used only used in morse code and digimode[?] transmissions and is therefore omitted during voice operations.

An example RST report for a voice contact would be "59", usually pronounced "five and nine," and symbolises a perfectly readable and very strong signal.