Intel 8251

The 8251 is a Universal Synchronous/Asynchronous Receiver/Transmitter packaged in a 28-pin DIP made by Intel. It is typically used for serial communication and was rated for per second signalling rate.
It is commonly confused with the much more common 8250 UART that was made popular as the serial port in the IBM Personal Computer.
It includes 5 sections 
Known uses.
The Intel 8251A was used in the Intel SDK-86 MCS-86 System Design Kit
and the DEC LA120 printing terminal.
The device is also used in the IC-10 RS-232 interface for Kenwood HAM radios like TS-440S, TS-711, TS-811 and many others.