As the electricity will kill you, don't stay on any of the letters while it is lit up. You have to time your jump to the letter 'H' while it is still electrified, landing just as it turns off. Then quickly jump to letter O, which will move a bit and let a rope swing from the letter 'T'. Then you will be able to reach the circuit breaker box on the other side of the chasm, return back and hop through the letter once more.