Acromag

Adjacent Channel Rejection	When a radio can be set to operate at multiple frequency channels, there will be two adjacent channels, one on each side of the selected channel. These two channels will operate at the next lower frequency and the next higher frequency. The adjacent channel rejection is the ability of the receiver to operate on the selected channel when a stronger signal is present on an adjacent channel. It is measured as the highest ratio of the signal level on the adjacent channel to the signal being received on the selected channel.
ARC4 (Alleged RC4)	This encryption method is a stream cipher with a variable key size (40 or 128 bit keys). The design also implements a hashing algorithm to eliminate weak key combinations.
ASCII	American Standard Code for Information Interchange; a Modbus communication mode. In ASCII mode, each eight-bit byte in a message is sent as two ASCII characters. The main advantage of this mode is that it allows time intervals of up to one second to occur between characters without causing an error. (See also RTU mode)
Broadcast	A single master radio communicates with two or more remote radios, but the remote radios do not communicate directly with each other. Any radio that sends data over the air will be sent to all radios within the network. The only radio that responds is the one that is attached to the device that is being addressed. The application layer (Layer 7) will respond to the message.
Channel Data Rate	There are two types of signal transmissions with these transceivers, serial (wired) and radio (wireless). The maximum serial channel data rate is 115.2kBaud. For a signal that is transmitted wirelessly between two radios, the Channel Data Rate is 250kbps. This is calculated from twice the Full-Duplex rate (115.2KBaud), which is the Nyquist rate, plus a buffer for timing packets from radio synchronization.
Configuration PC	A computer that contains the OS2400 Setup/Diagnostic software.
dBi	Decibels referenced to an "ideal" isotropic radiator in free space; frequently used to express antenna gain.
dBm	Decibels reference to one milliwatt (mW); an "absolute" unit used to measure signal power (transmit power output or received signal strength).
DCE	Data communications equipment. For example, a modem.
Decibel (dB)	A measure of the ratio between two signal levels; used to express gain (or loss) in a system.
Default Gateway	The default network that the Configuration PC will operate on. The gateway routes the traffic to/from the outside network.
DTE	Data Terminal Equipment. For example, a computer or terminal.
Effective Isotropically Radiated Power (E.I.R.P.)	The arithmetic product of the power supplied to an antenna and it's gain.
Failsafe Networks	Most requests for failsafe Profibus network configurations are concerned about using two CPU’s and one network cable with I/O that can “failsafe” in the event of a catastrophic network communication loss. All Acromag 98xPB and 97xPB Discrete and Analog Output Modules have outputs that may be configured to fail in the last state or predefined state in the event of network communications which support “failsafe” systems.
Firmware	The embedded software code that is in the radio to direct radio function (similar to the BIOS in a personal computer). This is distinguished from the setup/diagnostic application software that is installed on the configuration PC.
Frequency Hopping	A radio that rapidly changes it's operating frequency several times per second following a pre-determined sequence of frequencies. The transmitting and receiving radios are programmed to follow the same frequency hopping sequence.
Full-Duplex	Simultaneous two-way independent transmission in both directions.
Half-Duplex	A circuit designed for transmission in either direction but not both directions simultaneously.
Hop Patterns	The OS2400 radios are capable of supporting up to 32 networks of 2000 radios each and the networks will not interfere with each other. This is accomplished through a pseudo random combination of frequency sets and hop sequences defining the network channels which are defined as hop patterns.
IP Address	An identifier for a computer device in a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 1.160.10.240 could be an IP address.
ISM Band	FCC Part 15 rules specify unlicensed use of Spread Spectrum devices in the 900MHz, 2.4GHz and 5.8GHz bands for Industrial, Scientific and Medical (ISM) purposes. One watt maximum transmit power in the USA.
Latency	Radio network latency is defined as the additional time a message takes to transfer between two devices while passing through the radio network compared to a wire connection. It can be measured as the time between the first character of a message reaching the source radio's RXD pin and the same character reaching the destination radio's TXD pin. In the OS2400, the latency is less than 20mSec.
Link Point	The graphical point next to a radio icon in the setup software. RF communications between radios is called an RF link and is represented as a graphical black line between the radio's link points.
Modbus	This protocol provides the internal standard that Modbus ready devices use for parsing messages. During communications on a Modbus network, the protocol determines how each device will know it's address, recognize a message addressed to it, determine the kind of action to be taken and extract any data or other information contained in the message. If a reply is required, the device will construct the reply message and send it using Modbus protocol.
Modem	Stands for MODulator-DEModulator. A device that converts digital signals to analog signals and vice-versa. Analog signals can be transmitted over communications links such as telephone lines.
Network Master Device	A device that is connected to the master radio.
Network Slave Device	A device that is connected to a remote radio.
Null Modem Cable	A specialty cross-communication cable with female connectors on each end used for direct connection between devices when no modems are present. Commonly used as a quick and inexpensive way to transfer files between two PCs without installing a dedicated network card in each PC.
Peer-to-Peer Network	Each radio in a peer-to-peer network has the ability to receive data from, and transmit to, any other radio in the network.
Point Multipoint (Modbus) Network	A network with a single master radio and multiple remote radios. The devices cabled to the radios communicate through the Modbus standard which is a Command/Response protocol. The master radio sends command data to a remote radio based on the Modbus address of the individual device. The data is only sent to one address at a time. Each remote radio responds by sending it's data back only to the master radio.
Point-Multipoint (Broadcast) Network	A network type where a single master radio sends data to every remote radio in a network. This is done repeatedly until every remote radio individually receives and acknowledges the data. Each remote radio sends pending data back to the master radio. In this configuration, there are multiple remote radios referenced to a single master radio.
Point-to-Point Network	A network consisting of a single master radio and a single remote radio. All data from the master is received and acknowledged by one remote. All data from the single remote is received and acknowledged by the master radio.
Poll	The act of electronic communication.
Protocol	Rules that define how two or more devices will communicate with each other.
Receiver Sensitivity	A measurement of the weakest signal a device can receive and still correctly translate it into data. Also, the minimum required radio frequency (RF) signal power to meet a certain performance level. This level is referred to as the bit error rate (BER) and could be in the form of -80dBm or 0.000000010mW.
Redundant Networks	Systems requiring complete redundancy typically intend to double their cpu, network communications cable, and I/O counts. Since Acromag’s 9xxPB I/O modules are very economical and compact, it is now feasible from a budget and space perspective to use twice the amount of I/O for fully redundant system requirements. Remember, Acromag’s 9xxPB I/O modules don’t require the cost or space of buscouplers, racks, or special power supplies.
Repeater	On RS485 physical layers, this is a device used to provide gain or boost to a signal which is shared by more than 32 devices or transmitted farther than 4000 feet.
RTU (Remote Terminal Unit)	Modbus transmission mode where each eight-bit byte in a message contains two four-bit hexadecimal characters. There are two transmission modes, ASCII and RTU. The main advantage of the RTU mode is that it's greater character density allows better data throughput than the ASCII mode for the same Baud rate. Each message is transmitted in a continuous stream.
Simplex	A circuit capable of operating in only one direction.
Spread Spectrum	A technique where a narrow-band signal is spread over a broader portion of the radio frequency band.
Spurious Rejection	A Spurious signals are transmissions at frequencies outside of the radios normal operating frequency range. Spurious rejection is the ability of the receiver to operate in the presence of these spurious signals. It is measured as the highest ratio of the spurious signal to the signal level being received correctly.
Store & Forward Repeater Network	When repeater radios are used in a network, the maximum data rate is 57.6 kbps (at 115.2k Baud Rate) due to the repeater spending half of the time communicating forward and half of the time communicating in reverse. A repeater radio can also interface to a device and act as a remote radio at that location.
Subnet Mask	A mask used to determine what subnet an IP address belongs to. An IP address has two components, the networking address and the host address. For example, consider the IP address 150.215.017.009. Assuming this is part of a Class B network, the first two numbers (150.215) represent the Class B network address and the second two numbers (017.009) represent the Class B host address.