needs to activate collar

His body swayed slightly as he stood there with his modern cane.
He moved to push the electrode switch with the tip of the gun in his left hand, but...

“That’s your weakness, isn’t it?”
Someone grabbed his hand from behind.
“No matter how strong your power is, you can’t activate it without pressing that switch,
hm?”
Before Accelerator could get his hand free, a heavy blow came to the side of his head. It
wasn’t the feeling of being punched by a fist. It was a dull feeling that felt like being hit
by a metal pipe or hammer.
He felt a liquid oozing from the side of his head.

- Toaru Majutsu no Index Volume 15, Chapter 2 Part 12