was formally included as part of the standard (it was only referenced in the appendix of RS-232-C). The voltage range was extended to ±25 volts, and the circuit capacitance limit was expressly stated as 2500 pF. Revision E of EIA-232 introduced a new, smaller, standard D-shell 26-pin "Alt A" connector, and made other changes to improve compatibility with CCITT standards V.24, V.28 and ISO 2110. Specification document revision history: EIA RS-232 (May 1960) "Interface Between Data Terminal Equipment & Data" EIA RS-232-A (October 1963) EIA RS-232-B (October 1965) EIA RS-232-C (August 1969) "Interface Between Data Terminal Equipment and Data Communication Equipment Employing Serial Binary Data Interchange" EIA EIA-232-D (1986) TIA TIA/EIA-232-E (1991) "Interface Between Data Terminal Equipment and Data Communications Equipment Employing Serial Binary Data Interchange" TIA TIA/EIA-232-F (October 1997) ANSI/TIA-232-F-1997 (R2002) TIA TIA-232-F (R2012) Limitations of the standard Because RS-232 is used beyond the original purpose of interconnecting a terminal with a modem, successor standards have been developed to address the limitations. Issues with the RS-232 standard include: The large voltage swings and requirement for positive and negative supplies increases power consumption of the interface and complicates power supply design. The voltage swing requirement also limits the upper speed of a compatible interface. Single-ended signaling referred to a common signal ground limits the noise immunity and transmission distance. Multi-drop connection among more than two devices is not defined. While multi-drop "work-arounds" have been devised, they have limitations in speed and compatibility. The standard does not address the possibility of connecting a DTE directly to a DTE, or a DCE to a DCE. Null modem cables can be used to achieve these connections, but these are not defined by the standard, and some such cables use different connections than others. The definitions of the two ends of the link are asymmetric. This makes the assignment of the role of a newly developed device problematic; the designer must decide on either a DTE-like or DCE-like interface and which connector pin assignments to use. The Handshaking and control lines of the interface are intended for the setup and takedown of a dial-up communication circuit; in particular, the use of handshake lines for flow control is not reliably implemented in many devices. No method is specified for sending power to a device. While a small amount of current can be extracted from the DTR and RTS lines, this is only suitable for low-power