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SYSTEM OVERVIEW MANUAL
MODEL 64000
RS-232-C/Current Loop Communications
EIA RS-232-C Interface Standard
Most voltage interfaces in North America conform to the EIA RS-232-C I nterface Standard.
This specifies a 25-pin connector as the standard interface in data communication networks,
with lettered pin assignments for ground, data, control and timing circuits. The interface also
specifies the mechanical and electrical requirements of an interface, within an operating
range of 0 to 19,200 bps in-bit-serial operation. It provides a common meeting ground,
allowing interaction between many types of equipment and manufacturers, providing great
flexibility in the selection of equipment for data communication networks.
Mechanical
The signal interface between the Data Communications Equipment (DCE), usually a
modem, and the Data Terminal Equipment (DTE), usually a remote terminal or data
processor, is located at the RS-232-C-specified connector located between equipment
Cables less than 50 feet (15 meters) are recommended for interconnection. Longer cables
may be used provided the load capacitance is suitable. The Model 64100A pin assignment
shown in table 2-9 must be used and unassigned pins may carry additional circuits
determined by mutual agreement between the communicating parties. Figure 2-33 is the
Model 64100A Development Station RS-232-C/Current Loop Schematic. Figure 2-34 is the
RS-232/Current Loop Interface.
Electrical
Except for protective and signal grounds, all circuits carry
bipolar low-voltage signals
suitable for electronic circuits. All voltages are measured at the connector with respect to
signal ground (AS) and cannot exceed +1- 25 V. The significance of the bipolar signals is
summarized in table 2-10, with the region between +1- 3 V defined as the transition region.
While RS-232-C designates 23 circuits, the number actually in use depends upon the type of
modem.
2-60
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