What was the primary limitation of the early acoustic signals installed for the blind in the 1920s?

Answer

They gave no information about the crossing location or when the 'Don't Walk' phase began.

These early acoustic signals only indicated when it was safe to cross (green light), but the user had to locate the pole first and received no information about when the crossing phase ended.

What was the primary limitation of the early acoustic signals installed for the blind in the 1920s?
inventionSafetySignaltrafficcrosswalk