Eia-232
communications, standard
(Formerly “RS-232”) The most common asynchronous serial line standard. EIA-232 is the EIA equivalent of ITU-T V.24, and V.28.
EIA-232 specifies the gender and pin use of connectors, but not their physical type. RS-423 specifies the electrical signals. 25-way D-type connectors are common but often only three wires are connected – one ground (pin 7) and one for data in each direction. The other pins are primarily related to hardware handshaking between sender and receiver and to carrier detection on modems, inoperative circuits, busy conditions etc.
The standard classifies equipment as either Data Communications Equipment (DCE) or Data Terminal Equipment (DTE). DTE receives data on pin 3 and transmits on pin 2 (TD). A DCE EIA-232 interface has a female connector. DCE receives data from DTE on pin 2 (TD) and sends that data out the analog line. Data received from the analog line is sent by the DCE on pin 3(RD).
Originally DCE was a modem and DTE was a computer or terminal. The terminal or computer was connected (via EIA-232) to two modems, which were connected via a telephone line.
The above arrangement allows a computer or terminal to be connected to a modem with a straight-through (2-2, 3-3) cable. It is common, however, to find equipment with the wrong sex connector or with pins two and three reversed, requiring the insertion of a cable or adaptor wired as a gender mender or null modem. Such an adaptor is also required when connecting a computer directly to a terminal or to another computer without the use of modems.
(1999-12-28)
Read Also:
- Eia-232c
communications, standard The EIA equivalent of ITU-T standard V.24. The EIA EIA-232C electrical signal is unbalanced +/- 5 to +/- 12V, polar non return to zero and handles data speeds up to 19.2 kilobits per second. [Correct name? Relationship to RS-232C? Difference from EIA-232?] (2004-08-02)
- Eia-422
communications, standard (Formerly “RS-422”) An EIA serial line standard which specifies 4-wire, full-duplex, differential line, multi-drop communications. The mechanical connections for this interface are specified by EIA-449. The maximum cable length is 1200m. Maximum data rates are 10Mbps at 1.2m or 100Kbps at 1200m. EIA-422 cannot implement a truly multi-point communications network (such as with […]
- Eia-423
communications, standard (Formerly “RS-423”) An EIA serial line standard which specifies single ended communication. The mechanical connections for this interface are specified by EIA-449. Although it was originally intented as a successor of EIA-232 it is not widely used. The EIA-232 standard has its limits at 20kbps and 1.5m. EIA-423 can have a cable lenght […]
- Eia-449
communications, standard (Formerly “RS-449”) An EIA standard for a 37-pin or 9-pin D-type connector (functional- and mechanical characteristics), usually used with EIA-422 or EIA-423 electrical specifications. (2002-10-05)
- Eia-485
communications, standard (Formerly “RS-485”) An EIA serial line standard which specifies 2-wire, half-duplex, differential line, multi-point communications. Maximum cable length is 1200m. Maximum data rates are 10Mbps at 1.2m or 100Kbps at 1200m. EIA-485 can implement a truly multi-point communications network, and specifies up to 32 drivers and 32 receivers on a single (2-wire) bus. […]