| TIA-485-A (Revision of EIA-485) | |
|---|---|
| Standard | ANSI/TIA/EIA-485-A-1998 Approved: March 3, 1998 Reaffirmed: December 7, 2012 |
| Protocol information | |
| Physical media | Balanced interconnecting cable |
| Network topology | Point-to-point, multi-dropped, multi-point |
| Maximum devices | At least 32 unit loads |
| Maximum distance | Not specified |
| Mode of operation | Different receiver levels: binary 1 (OFF) (Voa–Vob < −200 mV) binary 0 (ON) (Voa–Vob > +200 mV) |
| Available signals | A, B, C |
| Connector types | Not specified |
RS-485, also known as TIA-485(-A) or EIA-485, is a standard, originally introduced in 1983, defining the electrical characteristics of drivers and receivers for use in serial communications systems. Electrical signaling is balanced, and multipoint systems are supported. The standard is jointly published by the Telecommunications Industry Association and Electronic Industries Alliance (TIA/EIA). Digital communications networks implementing the standard can be used effectively over long distances and in electrically noisy environments. Multiple receivers may be connected to such a network in a linear, multidrop bus. These characteristics make RS-485 useful in industrial control systems and similar applications.