Another palm to the side of the head moment

I may or may not need new batteries for the grader. I hadn't used it since I cleaned the battery terminals and cables about a week ago. I had to boost it then. I was using the dump truck today where you turn the key and push a black button to start it. I got in the grader and turned the key. I heard the buzzer for low oil pressure. Then I pushed the black button and nothing so I hooked my truck up to boost it. I talked to a couple guys that came out to ride. 15 minutes later I figured I'd try the grader. I hit the black button again and nothing. Then it dawned on me that was the horn button and it didn't work. I turned the key to start and it fired right up. Duh, now I don't know if the batteries are getting weak or not. Must have been so happy the dump truck keeps running after pushing the black button I totally forgot the grader starts with the key. I was thinking something was wrong with transmission and it wasn't registering it was in neutral.