See attached image. This is part of a one-line diagram of a solar-with-battery backup power supply system. Two inverters, one for the batteries and one for the solar panels, feed these things (one of which I've circled in red) at the inputs to a splitter, which splits the load between the two sources. I think the mystery symbol represents a current or power sensor integral to the splitter, but I'm not sure. The drawing was made by a Canadian and therefore contains a mix of American and European symbols, but the client was in Tanzania, so it could be African as well. We use the client's country's symbols if we know them.