The termination also includes pull up and pull down resistors to establish fail-safe bias for each data wire for the case when the lines are not being driven by any device. Although many applications use RS-485 signal levels, the speed, format, and protocol of the data transmission are not specified by RS-485. This way, the lines will be biased to known voltages and nodes will not interpret the noise from undriven lines as actual data; without biasing resistors, the data lines float in such a way that electrical noise sensitivity is greatest when all device stations are silent or unpowered. Star and ring topologies are not recommended because of signal reflections or excessively low or high termination impedance. The value of each termination resistor should be equal to the cable characteristic impedance (typically, 120 ohms for twisted pairs). Ideally, the two ends of the cable will have a termination resistor connected across the two wires.

This allows RS-485 to implement linear bus topologies using only two wires. 2) the GSM version also allows you to indicate a possible PIN (leave blank if there is no PIN) and the operator's APN (possibly you can search for it on Google). Utilizing a series of dedicated interface devices, rs485 cable it allows PCs and industrial controllers to communicate. These are used in programmable logic controllers and on factory floors. If a star configuration is unavoidable, special RS-485 repeaters are available which bidirectionally listen for data on each span and then retransmit the data onto all other spans. It has a special capacitive sensor designed by us, efficient and of good precision, waterproof, resistant to oxidation and not subject to variations due to salinity and soil composition: better than this there are only the "extraction pressure" sensors (which we do not propose because they are not durable and also the sensor alone costs hundreds of euros).

PC environment. 8P8C modular connectors are used in this case. The two values provide a sufficient margin for a reliable data transmission even under severe signal degradation across the cable and connectors. Circuits may be terminated on screw terminals, D-subminiature connectors, or other types of connectors. In a computer system, SCSI-2 and SCSI-3 may use this specification to implement the physical layer for data transmission between a controller and a disk drive. RS-485 signals are used in a wide range of computer and automation systems. Converters between RS-485 and RS-232 are available to allow a personal computer to communicate with remote devices. In theatre and performance venues, RS-485 networks are used to control lighting and other systems using the DMX512 protocol. Digital communications networks implementing the standard can be used effectively over long distances and in electrically noisy environments. This connection may be used to limit the common-mode signal that can be impressed on the receiver inputs.

Without termination resistors, signal reflections off the unterminated end of the cable can cause data corruption. It requires minimal wiring and can share the wiring among several seats, reducing weight. RS-485 is also used in building automation as the simple bus wiring and long cable length is ideal for joining remote devices. As a rule of thumb, the speed in bit/s multiplied by the length in metres should not exceed 108. Thus a 50-meter cable should not signal faster than 2 Mbit/s. SC, G or reference, the common signal reference ground used by the receiver to measure the A and B voltages. It also defines three generator interface points (signal lines); A, B and C. The data is transmitted on A and B. C is a ground reference. Section 4 defines the electrical characteristics of the generator (transmitter or driver), receiver, transceiver, and system. RS-485 only specifies the electrical characteristics of the generator and the receiver: the physical layer. RS-485 is used as the physical layer underlying many standard and proprietary automation protocols used to implement industrial control systems, including the most common versions of Modbus and Profibus. RS-485 serves as a physical layer for the AES3 digital audio interconnect.