A high-low signal in the trump suit. In the trump suit, an echo shows an odd number (ie opposite to a standard signal in a plain suit) and usually a desire to ruff.
In the first trump suit, declarer plays the ace and then up to the queen. If West plays the six followed by the two, this shows a third trump and strongly suggests a desire for a ruff.
In the second, declarer cashes the ace-king. Here West might play high- low even with no desire to ruff. When declarer stops drawing trumps, East can infer that either West has no more trumps or that West’s remaining trump is a winner. West’s trump echo tells East which it is.