The below image is from a service manual for a mobile radio. Note the small symbols that appear to be four triangles, point to point. I've searched far and wide and cannot identify that symbol. I have a nagging feeling that I've seen something like it in hydraulics, but never in an electronics diagram. I know that my radio doesn't have a bunch of stars of David printed inside it, so what could this symbol be?
Some of them have a line through the middle, others don't. Compare for example the ones near the labels "mic int" and "mic ext". Does this represent something, or is it a typo?