RS-232 connection
The DART 200 has an RS-232 DB9 interface. If the remote device has a similar interface, then any standard PC communications cable functions as a connector between the two. Otherwise, refer to Data and control interface, p. 8-14, for a discussion of the RS-232 leads and the minimum number required for operation.
Standard RS-232 communications cables function properly for distances up to 50 feet. If longer lengths are required, low loss RS-232 cable or electronic cable extenders can be used; both are available from local cable distributors or electronic catalogs.
Null modem function
The RS-232 interface specification was defined before the invention of microcomputers. The original intent was to standardize the method that computers and terminals used to communicate remotely over telephone lines. The standard specification is generalized in Figure 6-1.
Figure 6-1. Standard RS-232 connection
The RS-232 standard specified the label Data Terminal Equipment or Data Terminating Equipment (DTE) for terminals and computers, and the label Data Communications Equipment (DCE) for modems. The popularization of RS-232 serial communications resulted in many different types of equipment, besides modems, that employ the standard. Many manufacturers expect devices to connect directly to DTE equipment (usually, PCs). Consequently, devices are designed with a DCE interface, so a standard RS-232 cable meets the cabling requirements. Common usage of RS-232 is shown in Figure 6-2.
