Hello I have question. I read one book and there is that crews o m13/40 comunicated by some interpol or use navy style telegraph or intercom. And that driver wasnt conected to the itercom so I dont know how did the crew comunicate and what did they use because I cant find any photo or page how did the 2 systems worked or looked like and who did use what? Thanks for asnwer if you can find any photos and descriptions how that worked and what was interpol for and Telegraph for