Due to the various differences and contradictions in RS-232 implementations, it is not very easy to decide which appropriate cable to use to connect two communication devices. Connecting DCE and DTE devices with the same type of connector requires a direct cable with a suitable end point. Bump converters are used to resolve gender mismatches between cables and connectors. Connecting devices with different connectors requires different cables to connect the appropriate pins according to the table above. It is common for a cable to have 9 pins on one end and 25 pins on the other, and manufacturers of equipment with RJ-45 type connectors usually provide cables with DB-25 or DB-9 connectors (or sometimes swappable cables with connectors that allow multiple devices to work).
Connecting two DTE devices requires a virtual modem to act as a DCE to exchange the appropriate signals (TD-RD, DTR-DSR, and RTS-CTS). This can be accomplished by a separate device plus two cables or by using a single cable.
The virtual modem in the Yost standard is a fully reversed cable, which flips pins 1 through 8 on one port to connect to pins 8 through 1 on the other port (not to be confused with Ethernet twisted-pair cable, which is wired very differently).
To configure and diagnose the RS-232 cable, a wiring splitter can be used. Wiring taps have recessed RS-232 connectors that allow for inline wiring, and provide lights that correspond to each pin, as well as various configurations for connecting the pins.
RS-232 cables and many connectors can be found at electronics stores, and cables may be from 3 to 25 pins, with 4 to 6 pins for typical applications. Flat RJ (phone line type) cables can be used with specialized RJ-RS-232 connectors, which are the easiest to configure.
The reason the bi-directional interface can be made with only 3 wires is because all the signals of RS-232 *** enjoy a common *** ground. The unbalanced circuitry makes RS-232 very susceptible to base point voltage offsets between the two devices. RS-232 also has only relatively poor control over the rising and falling periods of the signal and is susceptible to crosstalk.RS-232 is recommended for communication over short distances (up to 15m). Because of the asymmetric circuitry, RS-232 interface cables are usually not made from twisted pair wire.
Some devices also require a "handshake" protocol, e.g., pin 20 is generally used to indicate "device ready". Pins can also be skipped or picked up from the connector. For example, a pin on device A sends a signal asking "Are you ready?". Suppose device B does not send such an indication. The handshake pins for the public *** are 20, 8, 4 and 6.