the standard, but guidance is given in its annex. (This annex is not a formal part of the standard, but is included for information purposes only.) Limitations on line length and data rate varies with the parameters of the cable length, balance, and termination, as well as the individual installation. Figure A.1 shows a maximum length of , but this is with a termination, and the annex discusses the fact that many applications can tolerate greater timing and amplitude distortion, and that experience has shown that the cable length may be extended to several kilometers. Conservative maximum data rates with 24AWG UTP (POTS) cable are 10 Mbit/s at to 90 kbit/s at , as shown in the figure A.1. This figure is a conservative guide based on empirical data, not a limit imposed by the standard. RS-422 specifies the electrical characteristics of a single balanced signal. The standard was written to be referenced by other standards that specify the complete DTE/DCE interface for applications which require a balanced voltage circuit to transmit data. These other standards would define protocols, connectors, pin assignments and functions. Standards such as EIA-530 (DB-25 connector) and EIA-449 (DC-37 connector) use RS-422 electrical signals. Some RS-422 devices have 4 screw terminals for pairs of wire, with one pair used for data in each direction. RS-422 cannot implement a true multi-point communications network, such as with EIA-485, since there can be only one driver on each pair of wires. However, one driver can fan-out to up to ten receivers. RS-422 can interoperate with interfaces designed to MIL-STD-188-114B, but they are not identical. RS-422 uses a nominal 0 to 5-volt signal, while MIL-STD-188-114B uses a signal symmetric about 0 V. However, the tolerance for common-mode voltage in both specifications allows them to interoperate. Care must be taken with the termination network. EIA-423 is a similar specification for unbalanced signaling (RS-423). When used in relation to communications wiring, RS-422 wiring refers to cable made of 2 sets of twisted pair, often with each pair being shielded, and a ground wire. While a double-pair cable may be practical for many RS-422 applications, the RS-422 specification only defines one signal path and does not assign any function to it. Any complete cable assembly with connectors should be labeled with the specification that defined the signal function and mechanical layout of the connector, such as RS-449. Applications One of the most widespread