Date of first black and white television broadcast?

The first public demonstration of electronic television using a mechanical scanning system was on July 2, 1927, by Philo Farnsworth in San Francisco. However, this was not a broadcast in the true sense, as it was a demonstration in a laboratory.

The first regular public television broadcasts began in 1928 in the United Kingdom, but these were still using mechanical scanning systems. The first public broadcasts using electronic scanning systems (which is the technology used in modern television) began in 1936 in the United Kingdom and the United States.

So, depending on how you define "first black and white television broadcast," the answer could be either 1927, 1928, or 1936.