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For more information, refer to the B B RS-422/485 Application Note. RS-422 Connector - This is the connector type used on the RS-422 side of a converter or device. RS-422 Port - A serial port which provides RS-422 differential inputs for receive and outputs for transmit. Typical RS-422 ports support 2-channels. RS-422 Transmit Enable - Some RS-422 devices can have the transmit driver enabled and disabled as is done for RS-485. Disabling the transmitter when not used saves power on port powered devices. It also allows a RS-422 device to operate as in a 4-wire half 485 mode, the same as a 4-wire RS-485 device. laptop battery

Normal RS-422 devices have the transmitter enabled all the time. Controlled transmitters are activated by setting the RTS line in the RS-232 device or the RTS control in the UART. When the RTS line is not asserted, the transmitter is set Off to a high impedance state. thinkpad

- RS-485 is a multi-drop extension to the RS-422 standard. It uses differential signals on twisted pairs for receive and transmit. RS-485 systems can be half duplex 2-wire systems (one twisted pair plus signal common/ground) or full duplex 4-wire systems. A RS-485 transmitter driver is activated to send data and is set to a high impedance tri-state at the end of transmission. Driver control can be automatic using a Send Data circuit, or manual by setting the RTS line or UART RTS control high for transmit, then low at the end of transmission. In a half duplex 2-wire system, the receiver is set to receive except when transmitting. microsoft

In a 2-wire system, all slaves and masters are normally in the receive mode. When one master transmits, all slaves and masters receive the signal and response, and all slaves must be able to ignore commands and responses to/from other slaves. Each slave must wait until transmit is finished plus a delay (for bus turn-around), before responding. laptop computers

In a 4-wire system, all slaves are connected to the transmitter of the master(s). All slaves connect to the receiver of the master(s). Each slave must respond only to commands addressed to it, but no turn-around delay is needed. The slave can start responding immediately, even while receiving. Other slaves never hear each other s responses. laptop computer

- This is the connector used on the RS-485 side of the converter or device. RS-485 Fail-Safe Port Isolator - A device intended for use in a RS-485 network to isolate a node which has become stuck in a MARK or SPACE state or which has lost power and is loading down the rest of the 485 network so other devices cannot be accessed. When a node stops working, the Port isolator disconnects it from the remainder of the network. desktop computer

- The RS-485 wiring and slave devices interconnected to one or more masters. The number of devices on a RS-485 network is only restricted by the addressing scheme of the devices, typically 255 for a single byte address. Up to 32 nodes can be tied directly together before a repeater or isolated repeater is required. RS-485 Port - Electrical connections that provide 2-wire half duplex RS-485 signals or 4-wire full duplex RS-485 signals. notebooks

- A low voltage implementation of RS-232 in which the maximum signal level is 3.5 volts. RTS - Request To Send - a RS-232 port handshaking line that is typically asserted (raised high) to notify another device that the asserting device would like to transmit data. Is also used in some applications to indicate that the asserting device is ready to accept data. lenovo

Some RS-422 and RS-485 Converters use RTS to enable transmit when Asserted (RTS High), and in 2-wire RS-485 systems to disable receive. When RTS is Low, receive is enabled, transmit is tri-stated off. Special software is required to use RTS control. Compare to automatic Send Data(SD). hard drive

- Receive or receiver - when Morse code was used, the letter X was commonly keyed rather than the full word, Rx rather than receiver, Tx rather than transmit/transmitter. Label for receive line pinouts. S-Registers - A set of registers in a modem that can be accessed with a special control sequence in order to control certain modem parameters outside the compatible command set. By setting S-register sequences each time the modem is started, a standard operating mode can be established. travelstar

- Society of Automotive Engineers - One useful function of such engineering societies is to establish and promote standards that can be adopted by members and industry without regard to a particular manufacturer or product brand. SAE J1939 - A CAN (Controller Area Network) based communications protocol. The J1939 is broken down into subsets used in the heavy trucks, agriculture, and industrial equipment industries. gateway

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1. Security related products include serial controlled video cameras, remote controlled camera housings, video recorders, Digital Time Lapse Recorders, VCRs, badge readers, access control, security gate controls and related products. software

2. A device that responds only to commands that contain the security access code. hard drives

- Automatic Send Data control. Circuitry for a RS-485 transmit line driver which enables the transmit driver for transmit, then returns the transmit driver to a high impedance tri-state at the end of transmission. Sensors - Input devices which are used to sense temperature, pH, flow, pressure, level, light level, noise, proximity, capacitance, mass, frequency, rotation, speed, oxygen or other gasses, smoke, radiation, or related factors which can be detected/sensed. electronics

- The connector used for serial connections to/from a device is typically a standard type of DB9 or DB25, but various connector types may be used, RJ-11/RJ-12, 8-pin DIN, RJ-45 or DB37. Common serial ports are RS-232, but RS-422 or RS-485 ports are available using expansion cards or converters. A USB port is serial, but is generally called a USB port, for Universal Serial Bus since the port provides for external system expansion rather than internal expansion using ISA or PCI bus. USB is a host/device bus, not a device/device serial connection. canon

- A hub connects multiple serial port devices to a network. Serial Port - Usually a RS-232C serial port, but may be RS-422 or RS-485 connections. The electrical connections to a computer or device In a serial port, a byte of data is transmitted or received one bit at a time. Typical 8 bit data requires that 10 bits be transferred, one bit at a time. In a 8 bit parallel port, data is transferred 8 bits at once. desktop pc

A USB port is a special type of host computer serial port. USB devices can communicate with the host, but not with each other. SG / Signal Ground - Signal Ground (SG) is the signal common for a serial or similar connector. Single ended signals are referenced the common, and differential signal receivers require the common reference to establish the common level between transmitter and receiver. Signal Ground may be isolated from the grounds on other devices or may be connected by some device or devices to Earth or AC mains ground. Signal Ground may be used as a reference to the (-) minus side of a power supply. desktop computers

- Shared Interrupt Request (IRQs) lines - When several computer devices or PCI slots use the same IRQ, they are sharing it. Serial Cards with shared IRQs can use one IRQ for 1-4 serial port UARTs. Hardware IRQ sharing may require hardware and software support, else only one device can be actively using that IRQ at a time. Simplex Mode - Operating single direction or half duplex. A single fiber optic cable is a simplex cable. think pad

- A type of optical fiber with a very small core diameter that provides only one internal reflective path (mode) to transfer light. Light enters and leaves the fiber at only one angle. Because the light has only one path, the bandwidth can be much higher than for multi mode fiber. Because of it comparatively small core diameter, a laser light source is typically used. This makes single mode fiber popular for more bandwidth intensive applications, such as telecommunications. repair

- A device which responds to commands by performing some action or returning data. A slave does not send data until data is requested. Slave Port - In a Smart Switch, the master port is the controlling port which accepts commands and selects port A, B, C, or D for connection. The Slave port is the selected A, B, C or D. Smart Device - data recovery

A device which has a microprocessor is considered a Smart device. Without a microprocessor, it is a Dumb device. Smart Switch - A B B Electronics device that allows you to control or monitor multiple serial devices with a single port. Sometimes called a code activated switch or sharer Smart Switch / Port Combiner Mode - This mode allows the RS-232 slave ports to connect with the master by asserting the RTS or CTS. The way a slave connects with the master varies with the model of smart switch being used. The master, with a designated command string can also select a port in this mode of operation. cisco

- In the smart switch mode, the device connected to the master port controlls communication with the slave ports. The smart switch will constantly monitor the data flow looking for a command string to direct its operation. The command will instruct the switch to connect a specified slave port to send or receive data to the master. SMPTE - Society of Motion Picture and Television Engineers - One function of such societies is to discuss and establish standards which can be used by others working in the same areas. Well known SMPTE standards include time codes used to synchronize picture frames and sound for film or video production. Another standard recommends pinouts for RS-422 video editors and related video equipment. keyboard

- Female connector which accepts pins - Receptacle/jack Software Command - A sequence of bytes, which is recognized by a device as a command parameter data. The characters and sequence is unique for various devices. Common printer sequences start with Esc (27 decimal), other devices use non-printable characters (such as STX RTX) to mark the start and end of the data, and use printable characters to encode parameter data. Most B B device command sequences are 4-6 characters for the command and data. monitor

- A software controlled device must be controlled by custom software that specifies that particular device or the customer/engineer must provide for custom programming that controls the device according to application needs. Solder Pads - copper pads to solder wires to Spread Spectrum - A transmitted signal that rather than using a limited fixed FM or AM signal frequency or channel, spreads the signal over a wide spectrum/range of frequencies during transmission. The receiver concentrates/compresses frequencies during reception, then recovers the information. desktop

- A commonly used optical fiber connector for both Multi-mode and Single-mode fiber. Used in many LAN installations and is the standard connector supplied on B B fiber optic converters and cables. Stages of Protection - Surge protection stages - one stage is usually a Transient Voltage Suppressor that clamps or limits the maximum voltage by conducting positive or negative voltages above a threshold voltage to ground or to the connection at the other side. A second stage may be a fuse or resistor in series with the signal line before the TVS. Extremely strong voltages or currents my open the fuse or be dropped across the resistor. A third stage may be a gas discharge device or neon device which breaks down and conducts above 72-90 volts. This can discharge high static voltages. infosys

- The Command line in a parallel printer interface. When the strobe is not asserted, the printer ignores data or changes on the data lines. After a byte is output to the data port, the Strobe is asserted to tell the printer to read the data. When the printer starts to read and process the data, the printer sets the Busy line to busy state, then processes the data. At the end of processing, the printer toggles the Acknowledge to acknowledge state for a certain time, then returns to non-acknowledge state and clears the Busy line. The strobe line is then changed to non-strobe condition, and the next byte can be placed on the data bus. refurbished laptops

- Suppression limits the voltage on the input lines. Suppression attempts to clamp or conduct voltages between lines on one side of the suppressor. High voltages and heavy currents may exceed the rating of the device, causing it to short or open, which is one reason some current limiting may be provided by fuse or resistance. The suppressor may become faulty while attempting to protect, so it may need to be replaced after a heavy surge or lightning. wipro

- A abnormal current or voltage that exceeds the normal maximum rating of a device. Surge Protection - Protection of a device from abnormal currents or voltages so that it is not damaged, and will be likely to operate normally after the short term condition ceases. How Surge Protection Works - Illustration Surge Suppressor - lap top

A device which suppresses voltage or current surges on serial data lines, AC input power lines, telephone/Facsimile lines, or antenna/cable TV lines. Switching Power Supply - A power supply that operates by turning off/on rapidly (switching) to convert DC to AC at some frequency (usually 15.734KHz or less) that can use a small core transformer. The AC is then rectified back to DC. The DC voltages on the secondary side may provide feedback to the primary side for voltage regulation. The transformer provides isolation. Optical feedback isolates the secondary side from the primary side. A switching supply for AC line power usually converts the AC to DC before converting it back to higher frequency AC, then DC. Many AC supplies are designed for Worldwide power and handle 240/220/120/100 VAC at 50/60Hz. refurbished

A DC/DC converter is a switching supply. TCP/IP - A set of protocols that permit physical networks to be joined together to form an internet. TCP/IP combines the individual networks to form a virtual network in which individual hosts are identified not by physical network addresses but by IP addresses. TD - Transmit Data (Tx) - The Data Output line on a Computer/DTE device, the input line on a Modem/DCE device. memory

- The (-) line in a RS-422 (or 4-wire RS-485) transmit pair. This line is minus relative to the TD(B) line during a inactive or MARK state. TD(B)+ - The (+) line in a RS-422 (or 4-wire RS-485) transmit pair. This line is positive relative to the TD(A) line during a inactive or MARK state. Telco - Telephone Company - a modem or device intended for use with Plain Old Telephone Service (POTS) lines can use standard dial up telephone lines normally used for standard voice telephone. intel

- A Control that can be activated based on phone rings and/or DTMF (touch tones). Terminal Blocks - Connection terminals which provide electrical contacts for tinned stripped wires, with some means of tightening or loosening the connection to the wires. B B devices using terminal blocks have a hole to insert the wire, and a screw to tighten/secure it. The hole can usually accept one or two wires. Some surge protection devices use a Terminal Strip, usually called a barrier strip. It accepts wires with a three-quarter wrap around the screw or lug. as400

- Connecting a resistance at one or both ends of a cable to prevent reflections is called Termination. The proper termination resistance is equal to the characteristic impedance of the cable. Reflections travelling up/down the line can alter the signal and the effect can be similar to Ghosting of a TV signal. Typical RS-422/RS-485 cables may require a 120 ohm termination at each end of a cable run if reflections cause a problem. Termination (when needed) is normally installed on the receivers at each end. Some B B converters/cards provide selectable termination using a jumper or switch, others provide extra terminals in parallel for connection of termination. averatec

Common termination values for electronic devices varies by the type of device, 75 ohms for video or RF antenna, 300 ohms for twin lead, 50 ohm for coax, and other values of pull-up/pull-down termination for SCSI bus devices. hardware

A combination radio transmitter and receiver TTL - Transistor Transistor Logic - logic levels for TTL digital ICs are typically +5VDC and 0VDC. The logic low must be less than 0.6 volts, the high over +4 volts. Input levels in between may be indeterminate, resulting in outputs either high or low. TVS (Transient Voltage Suppressor) - A device that suppresses voltages by conducting either positive or negative voltages above the threshold voltage from one terminal to the other. Electrically, a TVS works like back-to-back Zener diodes. dual xeon

- A cable for serial communication which includes at least one twisted pair of two wires. May be shielded or may provide a separate ground wire. Tx - Transmit or transmitter - when Morse code was used, the letter X was commonly keyed rather than the full word, Tx rather than transmitter, xmit rather than transmitter xceiver rather than receiver or Rx for receive/receiver. Label for transmit line pinouts. storage

- Universal Asynchronous Receiver Transmitter. The main component of any serial interface card. Converts serial data to/from a parallel I/O bus on a microprocessor or PC. The most popular versions include transmit and receive FIFO (First In, First Out) buffers for faster data transfers with less CPU overhead Unbalanced Signal - Single-ended signal referenced to ground or common. Noise/hum picked up cannot be canceled, often requires shielding. Compare to differential or balanced outputs or inputs. In balanced signals, the outputs are 180 degrees out of phase, in-phase common mode noise is cancelled in the receiver. seagate

- Un-interruptible Power Supply - a back-up power source that provides power conditioning and back-up power when the main power is lost due to electrical storms or other causes. USB (Universal Serial Bus) - Universal Serial Bus - a limited range high speed serial bus standard used to expand or add functionality to a host computer. Permits connecting peripheral devices such as hard drives, printers, scanners, optical drives, real time video/audio devices or legacy serial or printer ports. computer sales

Requires drivers for the host Operating System or requires that the OS provide compatible drivers as part of the system software. Separate drivers usually required for MacOS or Windows OS. USB Hub - A USB host port expander that enables connection of more USB devices (up to 128 total) to a host USB port. Expansion is usually 3 or more ports. USB Type A Female (Connector) - computer hardware

- used for upstream connection toward host USB Type A Male (Connector) - USB Type B Female (Connector) - - used for downstream connection toward device(s) USB Type B Male (Connector) - - used for downstream connection toward device UTP - (Unshielded Twisted Pair) Connector - See RJ-45 VAC - Volts AC - AC is Alternating Current printers

- Volts DC - DC is Direct Current Voltage Spikes - A transient, very short term high voltage on a signal or power line. WAN - Wide Area Network Watchdog - Hardware device that monitors activity with a timer. If the monitored activity ceases for longer than the time period, times out and sets off a alarm or resets the device or reboots the computer. technology

- Usually Radio Frequency wave transmission/reception but may use Infrared wave signals. Wireless Modem - RF modem X-ON/X-Off - Software handshaking commands used to start serial data flow and stop serial data flow. YAGI - A multi-element antenna which is sharply more sensitive to signals in the front direction, and much less sensitive to signals at the sides and rear. Elements at the rear are longer than the active elements. Elements at the front are shorter. The size and spacing of the elements is a function of the transmitted/received wavelength (frequency), antenna gain is compared to a dipole (3dB) or omni (0dB). Increased numbers of elements makes the antenna more directional and provides more gain in the front direction. mainframe

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