It had semaphores after it was electrified, as the NH used semaphores in the electrified territory. In fact, I think the last of the NH semaphores in the electrified territory were on the Harlem River Branch, the last being at Pelham Bay, until about the mid 1980's I think. Eventually all were replaced with regular PRR style position light (not color light) signals.
Some of these are visible in Astoria Park which is a good place to watch the Hellgate Bridge, there is several on a signal bridge just south of the span. Some are also visible from I-95 just south of New Rochelle in the wooded area adjacent to the hwy.
For more information, try the NH forum for more info...