What incident occurred on March 10, 1876, that facilitated the first successful transmission of intelligible speech?

Answer

He spilled battery acid onto his clothing while testing the liquid transmitter

During an experiment with a liquid transmitter, which used acid to vary the resistance of the electrical circuit, battery acid was accidentally spilled. This specific accident provided the necessary operating conditions for the transmitter to function effectively. It was during this event that the first coherent, articulate sentence, Mr. Watson—Come here—I want to see you, was successfully transmitted over the line.

What incident occurred on March 10, 1876, that facilitated the first successful transmission of intelligible speech?
inventionAlexander Graham BellTelephoneinventorinspiration