There were many chip producers that made UARTs compatible with those used in DLV11 pdp-11 QBUS SLU (serial line unit). ICs are: AY-3-1015, CDP6402, COM2017, HD6402, TR1602 and many others. You may read an article about these chips named: UARTs.PDF (see attachments below).
This is an example of usage: http://www.cs.ubc.ca/~hilpert/e/pdp11hack/index.html#hack