53 INT 53 - IRQ3 relocated by DESQview
53 INT 53 - IRQ3 relocated by IBM 3278 emulation control program, OS/2 v1.x
53 INT 53 - TI Professional PC - SVC INTERFACE
53 INT 53 - Tandy 2000 - SERIAL COMMUNICATIONS
53 INT 53 - WEB??? - API