The Poona Pact which was signed between the British Government and Mahatma Gandhi in 1932 provided for

The Poona Pact of 1932 was a compromise reached after Gandhi’s fast to oppose the Communal Award’s grant of separate electorates to the Depressed Classes. Under the Pact, separate electorates for Harijans (Depressed Classes) were abandoned and instead their representation was increased through reserved seats within the joint electorate — i.e., Harijan candidates would be elected by the general (joint) electorate but with seats earmarked for them. The Pact therefore replaced separate electorates with joint electorates carrying reservation and expanded the number of reserved seats for the Depressed Classes in provincial and central legislatures [2].

Sources

1. [1] Rajiv Ahir. A Brief History of Modern India (2019 ed.). SPECTRUM. > Chapter 19: Civil Disobedience Movement and Round Table Conferences > Ideological Differences and Similarities between Gandhi and Ambedkar > p. 400
2. [2] Rajiv Ahir. A Brief History of Modern India (2019 ed.). SPECTRUM. > Chapter 19: Civil Disobedience Movement and Round Table Conferences > Poona Pact > p. 392