The datasheet for the TI TPA3100D2 (a class D stereo power amp) contains a couple of these symbols in the block diagram on page 7:
I'm referring to the dotted circles around schematic lines. The arrows and highlighting were added by me.
The ROUTN, ROUTP, LOUTN, and LOUTP pins that those circles are near are the outputs of the amplifier. The circles are on a line connected to the "SC Detect" area of the fault block. I'm pretty sure that stands for "short circuit detect", since the chip does have that capability.
What are these symbols?