When was the first telephone introduced that was powered by batteries at the telephone exchange instead of using wet cell or dry cell batteries in the telephone?

The first telephone system powered by batteries at the telephone exchange, rather than using wet cell or dry cell batteries in the individual telephones, was introduced in 1892. This innovation significantly improved the efficiency and reliability of telephone systems, allowing for centralized power sources and reducing the maintenance burden on users. It marked a pivotal advancement in the evolution of telecommunications technology.