sentences:  Stored program control was invented by Bell Labs scientist Erna Schneider Hoover in 1954 who reasoned that computer software could control the connection of telephone calls.Proposed and developed in the 1950s, SPC was introduced in production electronic switching systems in the 1960s.The 101ESS PBX was a transitional switching system in the Bell System to provide expanded services to business customers that were otherwise still served by an electromechanical central office switch.