How is 3780 BSC/RJE emulation different from 3770 SNA/RJE emulation?
Fundamentally 3770 SNA/RJE and 3780 BSC/RJE terminals were designed to do the same job: namely, submit batch jobs from a remote location to an IBM mainframe computer. (Oddly the 3780 terminal came before the 3770 family.) 3780 BSC/RJE uses the bisync protocol while a 3770 RJE terminal uses the SDLC protocol (or other protocol supported by IBM’s SNA network). These protocols are mutually exclusive and therefore 3780 and 3770 terminals are not interchangeable.