This indicator shows "SSR" on the chart when SSR "Short Sale Restriction" is activated on the ticker. SSR "Short Sale Restriction" or "alternative uptick rule" is a rule introduced by the SEC that prohibits shorting on the bid when a stock has dropped more than 10% from the prior days close in the regular trading hours. It will stay activated for the day it has triggered and the following day through regular and extended market hours. Since this rule only applies to the US stock market it checks for the exchange and only displays it for US stocks.