I am troubleshooting an issue with an old motor generator system on a crane and I have a question. In the armature circuit there are two symbols that I cannot ID. They are in series with the generator and the motor. They are both in between the "BG" and "-H" symbols next to the "G", generator symbol and the "M" motor symbol. The second Pic is a close up of the symbol. I wonder what this is, and what its function is in the circuit. Thanks.
