A general term for a device that enables communication between networks or transmission systems that use different protocols. Protocol converters are often used in mainframe computing environments; they enable one device to emulate the communication functions of another device. For this reason, a protocol converter is sometimes known as an emulator, and it can be either hardware-based or software-based.
One type of protocol converter allows you to communicate asynchronously using a PC to a mainframe host over a synchronous communication link. You can thus use a PC as the front end to the host instead of using expensive synchronous terminals. The PC typically emulates a 3270 terminal for remote connections or a 5250 terminal for local connections.
For example, you can turn a PC into a 5250 terminal by installing a 5250 emulator card. Use twinax cabling to connect the port on the card directly to the AS/400 or System 390 mainframe. The 5250 emulator software running on the PC typically supports multiple concurrent 5250 sessions.
To support this synchronous/asynchronous conversion, the emulation hardware/software must perform several conversions:
Graphic P-13. Protocol converter.
You can also use protocol converters to connect ASCII printers to AS/400 or System/3x mainframe hosts. A protocol converter for this purpose is sometimes called a printer emulation card.