• Direct sequence data encoding with 16-bit security code (provides high immunity to noise and implements Futaba proprietary algorithms)
  
• Channel WatchTM technology (automatic clear channel search and select) – Futaba trademark
  
• Frequency hopping spread spectrum technology (FHSS)
  
• Direct sequence spread spectrum technology (DSSS)
  

• Hybrid spread spectrum technology (FH-DSSS)
  
• 2.4 GHz patch and diversity antenna designs
  
• Direct-conversion, super-regenerative, and super-heterodyne receiver designs
  
• AM, FM, ASK, FSK, and PSK modulation techniques
  

radio frequency (RF) – An electromagnetic frequency in the 20 kHz to 300 GHz range. They are divided into 8 general groups (VLF, LF, MF, HF, VHF, UHF, SHF, EHF) that constitute the radio frequency spectrum. Lower frequencies propagate more easily than higher frequencies. For example, sometimes you can listen to the same AM broadcast station (centered around 1 MHz) for hundreds of miles as you drive, contrasted with a TV station operating around 100 MHz which can only service a 40 to 50 mile radius. Microwave frequencies start at around 2 GHz and are best suited for unobstructed point-to-point communication (i.e. directly from one location to another) and for high-speed data transmission.

frequency channel – The specific radio frequency band (electromagnetic wave oscillation rate in hertz) that a radio control transmitter uses to broadcast its signal. The frequency channel denotes only the portion of the radio frequency spectrum that the system uses for communication and does not relate to the number of features it can control. Radio control systems that have multiple frequency channels allow multiple units to be operated independently in the same area without interfering with each other.

bandwidth – The size (in hertz) of the radio frequency range that a signal transmission occupies. Typical narrowband signals range on the order of kilohertz, while spread spectrum signals can occupy many megahertz of bandwidth.

narrowband – An imprecise term that typically refers to RF signals occupying on the order of 3 to 25 kHz of bandwidth in the radio frequency (RF) spectrum. Conventional RF signals (TV, radio, CB, etc.) are generally narrowband, which means that they emit all of their power in relatively narrow portions of the RF spectrum.

spread spectrum (SS) – A modulation technique that spreads data, by using a coding sequence, over an RF bandwidth wider than would normally be required by the content of the original data stream (data bandwidth). This technique provides high levels of communication reliability and security, and typically enables higher data transmission rates than are achieved with narrowband carriers. Two main types of spread spectrum techniques are frequency hopping and direct sequence.

direct sequence (DS) – A form of modulation (commonly used in spread spectrum communications) in which a code sequence is used to directly modulate a narrowband carrier (usually by phase-shift keying) and continuously distribute or spread the narrowband carrier over a much broader portion of an assigned frequency range. The code sequence is duplicated and synchronized at the receiver, where the signal is compressed or correlated back into its original narrowband form.

frequency hopping (FH) – A form of modulation (commonly used in spread spectrum communications) in which the transmitter and receiver (or transceivers) in a system synchronously change carrier frequencies (of narrowband waveform) rapidly based on a pattern derived from a code sequence. In this way, the data signal is spread over a broad RF band through the continual narrowband frequency "hopping".

simplex – Communication that takes place in only one direction on one communication channel. An example of simplex communication is a conventional pager. Data flow is from the transmission towers to the pager and not from the pager back to the transmission towers (new pager services now offer two-way capability).

half-duplex – A type of two-way communication in which both stations can send and receive signals or data but not at the same time. When one unit is sending, the other unit can only receive. An example of half-duplex communication is a two-way radio system such as the citizens’ band radio. While one person transmits, the person on the other end receives. The FRH series of wireless modems essentially use half-duplex transmission techniques, but simulate full-duplex communication by causing both units to switch very rapidly between transmit and receive modes (also referred to as time-division-duplex (TDD)).

full-duplex – A type of two-way communication in which both stations can send and receive signals or data at the same time. Full-duplex requires two communication channels, one operating in each direction. A telephone is an example of a full-duplex communication device since both parties can send and receive voice signals simultaneously.

operating range – The distance between the transmitter and receiver (or transceivers) at which communication between the two is still possible. Generally, if all other factors are equal, longer ranges equate to more expensive radio control systems.

antenna diversity – A method used to improve RF reception when multipath fading is present. This method uses two independent antennas, spaced at least 1/2 wavelength apart, to receive multiple incoming signals differing in phase or amplitude. The theory is that the signal will fade at one antenna while it increases at the other and the receiver selects the strongest.

multipath (fading) – Refers to the reception of the same transmitted RF signal from multiple paths, such as reception of the direct antenna-to-antenna signal and reception of a secondary signal that was reflected by surrounding structures. This phenomenon can cause signal fading (fluctuation in signal strength) due to interference between the RF signals arriving from multiple paths.

ARQ (automatic retransmission request) – A standard method of correcting transmission data errors used on virtually all high-speed data communication systems. The sender encodes an error-detection field based on the contents of the message (see CRC), and the receiver recalculates the field and compares it with the one it received. If they match, an acknowledgement (ACK) is transmitted to the sender. If they do not match, a negative acknowledgment (NAK) is returned and the sender retransmits the message.

CRC (cyclic redundancy check) – A process used to check the integrity of a block of data. The transmitting device generates a CRC value based on the number of 1's in the binary data block and transmits the CRC value with the data. The receiving device performs the same calculation on the received data and compares its result with the transmitted CRC value. If the values do not match, an error exists in the received data.

analog – A proportional change continuous in nature between states, like a dimmer switch for a light or the volume control on a radio.

digital – An abrupt or stepped change from one state to another, like an on-off switch for a light or the high beam switch on a car that changes the beam from one intensity to another in an abrupt step.

bit – A contraction of the words "binary digit". A bit is the smallest unit of digital information and is typically represented by a zero or one.

bps (bits per second) – The number of bits transferred per second.

byte – A contraction of the words "by eights" and represents a group of 8 bits.

channel – A control function of the radio system that can be analog or digital. Generally, if a switch or a pushbutton performs the function, then it controls a discrete or digital channel, while a joystick, knob, or dial typically controls an analog channel. The number of channels determines the total number of motions or features that can be controlled. For each control function required in the application, you need one channel. For example, a monorail hoist application that requires directional axis movements of +x, -x, +y, and -y would need a 4-channel remote control.

analog or proportional channel – A control function of the radio system where movement of a motor or servo being driven by the receiver is proportional to the movement of the input control (usually a joystick, but could be a knob) on the transmitter. If the proportional relationship is linear and the joystick/knob is moved to one-half of its full range, the servo will move to one-half of its total movement or the motor will rotate at one-half of its full speed.

digital channel – A control function of the radio system that toggles between two states. The control input at the transmitter is typically a manual toggle or pushbutton switch and the output is a relay (providing either dry contacts or switched voltage).

relay – A switch that is driven by an electrical signal, usually through a magnetic coil. When current is applied to the coil, an armature moves to push the switch contacts together. The contacts are pulled apart when the current is removed. This type of relay is referred to as "normally open" since the switch contacts are apart when the coil is not energized. Relays have specific voltage and current ratings for the coils and the contacts.

dry contacts – A type of relay output on Futaba's telecontrol receivers in which both relay switch contacts are made available for connection by the user. Neither of the contacts are connected internally to ground or any voltage sources.

switched voltage – A type of relay output on Futaba's telecontrol receivers in which one of the relay switch contacts is connected to the receiver's supply voltage internally while the other side is made available for connection by the user.

momentary output – An output mode wherein the receiver output relay closes when its corresponding switch on the transmitter is activated and remains closed until the switch is released.

latching output – An output mode wherein the receiver output relay closes when its corresponding switch on the transmitter is activated and remains closed until the same switch on the transmitter is activated again.

interlock latching output – An output mode wherein the receiver output relay closes when its corresponding switch on the transmitter is activated and remains closed until any of the other switches on the transmitter are activated. Activating the same pushbutton/switch will not open the relay.

wireless data communication system (WDCS) – A term used by Futaba to refer to a spread spectrum technology wireless modem that transmits and receives (referred to as a transceiver) serial data in digital form using radio frequencies. Sometimes also referred to as a radio data link, radio frequency modem, and radio modem. Two wireless modems are required to establish a wireless data link for communication.

serial data transmission – The most common method of sending data between data communication equipment. In this method, data is sent out in a stream, one bit at a time over one channel. The Electronic Industries Association (EIA) has developed several standards for serial data communication. Two of the most popular standards include the Recommended Standard 232C (RS-232C) and RS-485, with the RS-232 standard being the most dominant (used for communication between computers, terminals, and modems).

parallel data transmission – The transmission of a byte of data over multiple wires at one time that uses one data wire for each bit (along with other wires for signal control and timing). Data transmission is usually very fast when compared to serial data transmission but usually happens over much shorter distances.

RS-232C – An Electronic Industries Association (EIA) standard (also referred to as RS-232 and in its latest version EIA-232E) that specifies the electrical (ex. signal voltage levels), functional (ex. signal purpose), and mechanical interfaces (ex. connector types and pin assignments) for serial communication between computers, terminals and modems (DTE and DCE). The RS-232C interface is ideal for bit rates from 0-20 kbps and cable lengths up to 50 feet.

RS-422/485 – To overcome the cable length and bit rate limitations of RS-232C, the EIA developed the RS-422 standard, and later, an enhanced version, the RS-485. The RS-485 standard specifies only the signal levels, signal rates, cable characteristics, and driver/receiver specifications (the connector is undefined). Differential signaling (voltage difference between two lines is the data signal) provides for greater immunity to noise and allows bit rates up to 10 Mbps and cable lengths up to 4000 feet. Up to 64 devices can be interconnected (due to tri-state driver outputs), making this standard ideally suited for industrial multipoint applications, a configuration where one computer controls many different devices.

Data Transparent Mode – An operational mode of Futaba's wireless modems in which digital transmission between terminals occurs without the user or the equipment being aware of any special intermediate processing or equipment.

Packet Transmission Mode – An operational mode of Futaba's wireless modems in which a fixed number of bytes, consisting of both information and control data, are assembled and transmitted as a single unit or packet.

1:1, 1:n, n:m – Ratios that indicate network architectures. The ratio 1:1 indicates a network with only two nodes communicating with each other. The ratio 1:n indicates a network with one "master" node communicating with a variable number of "slave" nodes (also referred to as point-to-multipoint). The ratio n:m indicates a variable number of nodes communicating with a variable number of other nodes.

repeater – Equipment that is used extend the range or overcome obstacles and horizon constraints of RF communication systems. A repeater receives weakened signals and retransmits the same data at stronger signal levels. Futaba's wireless modems can be configured as repeaters allowing increased operation range between normally configured modems.