Equivalent pulse code modulation noise - Equivalent pulse code modulation noise In telecommunication, equivalent pulse code modulation noise (PCM) is the amount of thermal noise power on a frequency-division multiplexed (FDM) or wire channel necessary to approximate the same judgment of speech quality created by quantizing noise in a PCM channel. Note 1: The speech quality judgment is based on comparative tests. Note 2: Generally, 33.5 dBrnC ±2.5 dB is considered the approximate equivalent PCM noise of a 7-bit PCM system. Source: from Federal Standard 1037C and from MIL-STD-188.
Glossary of telecommunications transmission terms - see the Federal Standard article for copyright-related issues, as not all parts of the source document are in the public domain. Noise ambient noise level -- antenna noise temperature -- atmospheric noise -- background noise -- blue noise -- carrier noise level -- carrier-to-noise ratio (CNR) -- carrier-to-receiver noise density (C/kT) -- channel noise level -- circuit noise level -- closed-loop noise bandwidth -- C-message weighting -- cosmic noise -- effective input noise temperature -- equipment intermodulation noise -- equivalent noise resistance -- equivalent noise temperature -- equivalent pulse code modulation noise (PCM) -- equivalent satellite link noise temperature -- feeder echo noise -- flat weighting -- FM improvement factor -- FM improvement threshold -- front-end noise temperature -- HA1-receiver weighting -- idle-channel noise -- impulse noise -- in-band noise power.
List of electronics topics - 32VSB 4000 series 4VSB 555 741 7400 series 8VSB A Absolute gain Access control Acceptance pattern Access time Acoustic coupler Acquisition ADSL Adaptive communications Adder Adjacent-channel interference Alarm sensor Aliasing Alternate party Alternating current AM radio Amateur radio Ambient noise level American Radio Relay League (ARRL) AMI Ammeter Ampere Amplitude distortion Amplitude modulation Amplifier Analog Analog computer Analog decoding Analogue switch Analog to digital converter Angular misalignment loss Antenna Antenna blind cone Antenna effective area Antenna gain Antenna height above average terrain Antenna noise temperature Antenna theory aperiodic antenna aperture aperture illumination Aperture-to-medium coupling loss Apollo Guidance Computer Arithmetic and logical unit Armstrong oscillator ARRL Articulation score Astable Asynchronous communications system Asynchronous operation Asynchronous start-stop Atmospheric duct Atmospheric waveguide Attenuation Audible ringing tone Audio system measurements Automatic call distributor Automatic data.
Pulse-code modulation - Pulse-code modulation Pulse-code modulation (PCM) is a modulation technique. It is a digital representation of an analog signal where the magnitude of the signal is sampled regularly at uniform intervals of duration . Every sample is quantized to a series of symbols in a digital code, which is usually a binary code. Nyquist's theorem states that frequencies higher than half the sample frequency () cannot be reconstructed. PCM is used in digital telephone systems and for digital audio recording on compact discs. In telephony, several PCM streams may be multiplexed into a larger aggregate data stream. Table of contents showTocToggle("show","hide") 1 Digitization as part of the PCM process 2 Encoding the bitstream as a signal 3 History of PCM 4 See also Digitization as part of.
Jamming - aimed at radio signals to disrupt control of a battle. A transmitter, tuned to the same frequency as the opponents receiving equipment and with the same type of modulation, can with enough power override any signal at the receiver. The most common types of this form of signal jamming are: Random Noise; Random Pulse; Stepped Tones; Wobbler; Random Keyed Modulated CW; Tone; Rotary; Pulse; Spark; Recorded Sounds; Gulls; and Sweep-through. All of these can be divided into two groups - obvious and subtle. Obvious jamming is easy to detect as it can be heard on the receiving equipment, it is some type of noise such as stepped tones (bagpipes), random-keyed code, pulses, erratically warbling tones, and recorded sounds. The purpose of this type of jamming is to block out reception of.
Digital signal 0 - digital signaling rate of 64 kb/s, corresponding to the capacity of one voice-frequency-equivalent channel. The DS0 rate forms the basis for the North American digital multiplex transmission hierarchy. The DS0 rate may support twenty 2.4-kb/s channels, or ten 4.8-kb/s channels, or five 9.67-kb/s channels, or one 56-kb/s channel, or one 64-kb/s clear channel. To carry a typical phone call, the audio sound is digitized at an 8 kHz sample rate using 8-bit pulse-code modulation. Multiple DS0's are multiplexed together on higher capacity circuits. 24 DS0's make a DS1 signal, which when carried on copper is the well-known, T-carrier system, T1 (the European equivalent is an E1, containing 32 64 kbit/s channels). Source: from Federal Standard 1037C.
Radio - subjects named radio see radio (disambiguation). Radio is a technology that allows for the transmission of signals by modulation of electromagnetic waves. These waves travel (propagate) through the air and the vacuum of space equally well, not requiring a medium of transport. A radio wave is created whenever a charged object accelerates with a frequency that lies in the radio frequency (RF) portion of the electromagnetic spectrum. By contrast, other types of emissions which fall outside the RF range are gamma rays, X-rays, infrared & ultraviolet light, and light visible to humans. When a radio wave passes a wire, it induces a moving electric charge (voltage) that can be transformed into audio or other signals that carry information. Although the word 'radio' is used to describe this phenomenon, the transmissions which.
Public switched telephone network - the PSTN is a 64-kilobit-per-second channel, originally designed by Bell Labs, called a "DS0" or Digital Signal 0. To carry a typical phone call from a calling party to a called party, the audio sound is digitized at an 8 kHz sample rate using 8-bit pulse code modulation. The DS0's are the basic granularity at which switching takes place in a telephone exchange. DS0's are also known as timeslots because they are multiplexed together in a time-division fashion. Multiple DS0's are multiplexed together on higher capacity circuits, such that 24 DS0's make a DS1 signal, which when carried on copper is the well-known, T-carrier system, T1 (the European equivalent is an E1, containing 32 64 kbit/s channels). In modern networks, this multiplexing is moved as close to the end user as.
Pulse-amplitude modulation - Pulse-amplitude modulation Pulse-amplitude modulation is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. Pulse-amplitude modulation is now rarely used, having been largely superseded by pulse-code modulation, and, more recently, by pulse-position modulation. See also: Pulse-code modulation Pulse-position modulation Pulse-width modulation.
Pulse-width modulation - Pulse-width modulation Pulse-width modulation is a way to represent data over a communications channel. With pulse-width modulation, the value of a sample of data is represented by the length of a pulse. Pulses of various lengths (the information itself) will be sent at regular intervals (the carrier frequency of the modulation). _ _ _ _ _ _ _ _ Clock __ ____ ____ ____ ____ ____ ____ ____ ____ _ __ ____ ____ _ Data _________ ____ ___ ________ _ ___________ Data 0 1 2 4 0 4 1 0 The clock signal is not necessary as the leading edge of the data signal can be used as the clock if a small offset is added to the data value in order to avoid the lack.
Pulse-position modulation - Pulse-position modulation Pulse-position modulation is a form of signal modulation in which the message information is encoded in the temporal spacings between a sequence of signal pulses. This method is not used very frequently, because other methods are usually more suitable for typical data transmission, however one common use of PPM is for the radio control of model aircraft. Here the position of each pulse represents the angular position of an analogue control on the transmitter. The number of pulses per frame gives the number of controllable channels available. The advantage of using PPM for this type of application is that the electronics required to decode the signal is extremely simple, which leads to small, low weight receiver/decoder units, essential in model aircraft where every weight.
Noise-equivalent power - Noise-equivalent power Noise-equivalent power (NEP) is the radiant power that produces a signal-to-noise ratio of unity at the output of a given optical detector at a given data-signaling rate or modulation frequency, operating wavelength, and effective noise bandwidth. Note 1: Some manufacturers and authors define NEP as the minimum detectable power per square root bandwidth. When defined this way, NEP has the units of watts per (hertz)1/2. Therefore, the term is a misnomer, because the units of power are watts. Note 2: Some manufacturers define NEP as the radiant power that produces a signal-to-dark-current noise ratio of unity. The NEP measurement is valid only if the dark-current noise dominates the noise level. Source: from Federal Standard 1037C and from MIL-STD-188.
Frequency modulation - Frequency modulation FM redirects here, for alternate uses, see Fm Frequency modulation (FM) is the encoding of information in either analog or digital form into a carrier wave by variation of its instantaneous frequency in accordance with an input signal. This is typically accomplished using radio waves. The most typical use is radio broadcasting. Frequency modulation requires a wider bandwidth than amplitude modulation by an equivalent modulating signal, but this also makes the signal more robust against interference. Frequency modulation is also more robust against simple signal amplitude fading phenomena. As a result, FM was chosen as the modulation standard for high frequency, high fidelity radio transmission: hence the term "FM radio" (although for many years the BBC insisted on calling it "VHF radio"). An FM signal.
Morse code - Morse code Morse code is a system of representing letters, numbers and punctuation marks by means of a code signal sent intermittently. It was developed by Alfred Vail while he was helping Samuel Morse with Morse's invention of the telegraph (1835). Morse code is an early form of digital communication, however unlike modern binary digital codes that use just two states (commonly represented as 1 and 0), it uses five - dot, dash, short gap (between each letter), medium gap (between words) and long gap (between sentences). Table of contents showTocToggle("show","hide") 1 History of Morse 2 American Morse Code 3 Modern International Morse Code 4 Timing and representation 4.1 . 5 Letters, numbers, punctuation, prosigns 6 Commonly used Morse code abbreviations 7 Conversation with Morse code 8.
Modulation - Modulation In music, the term "modulation" means a key change. This article is about the concept of signal modulation in communications engineering. Modulation describes a range of techniques for encoding information on a carrier signal, typically a sine-wave signal. A device that performs modulation is known as a modulator. Modulation techniques include: Amplitude modulation (AM) Phase modulation (PM) Frequency modulation (FM) Single-sideband modulation (SSB) Vestigial-sideband modulation (VSB, or VSB-AM) Quadrature amplitude modulation (QAM) Orthogonal frequency division modulation (OFDM), also known as 'Discrete multitone modulation' (DMT) Wavelet modulation Ring modulation When OFDM is used in conjunction with channel coding techniques, it is described as 'Coded orthogonal frequency division modulation' (COFDM). Pulse modulation techniques include: Pulse-code modulation (PCM) Pulse-width modulation (PWM) Pulse-amplitude modulation (PAM) Pulse-position modulation (PPM) Where.
Digital - discrete counting. The distinction digital versus analogue can refer to data storage and transfer, the internal working of an instrument, and the kind of display. The word "digital" is commonly used in computing. Digital vs Analogue Digital noise When data is transmitted using analogue methods, a certain amount of noise enters into the signal. This can have a myriad of different causes: data transmitted via radio may get a poor reception, have interference from other radio sources, or pick up background radio noise from the rest of the universe. Electric pulses being sent down wires are impeded by the resistance of the wire, and heat variations can increase or reduce these resistances. Whilst digitally transmissions are also degregated, any slight variations can be safely ignored. Any variance could provide a great.
Disability etiquette - Disability etiquette Disability etiquette describes the code of rules for interacting with disabled people. For example: When you offer to assist someone with a vision impairment, allow the person to take your arm. This will help you to guide, rather than propel or lead, the person. (source: Easter Seals Disability Etiquette webpage) These rules have been developed based on the needs of disabled people, and to combat misconceptions widely held by the more able community. Lists such as the following, and close variants of them, are widely used in training people who deal with the general public (including people with disabilities) and are endorsed by a number of organizations. Even the existence of these lists may be offensive to some, since it tends to lump disabled people into a single group.
History of radio - FM interests said it would cost $75,000,000 to convert and that it would set back the medium for years, which it did. Of course the FM interests fought back, Edwin Armstrong began fighting in 1944 to keep the frequencies FM already had. Armstrong went to court and to Congress, but lost in court and in a Congress that paid him lip service and little else. In 1945 when the change was ordered, there were already 55 pioneer FM stations on the air, and no nonexperimental television stations. The Federal Communications Commission had its most extensive hearings to that date, September 28 to November 2, 1944, on allocations decisions. When the Federal Communications Commission was making these decisions it had to balance several factors, but because of the wartime freeze it had.
Frame (telecommunications) - underlying communication channel so that it can be used simultaneously for more than one transmission. Notionally, each frame is a slot which could be filled by a transmitted packet. In these schemes, not all frames are necessarily in use at once. In the multiplex structure of pulse-code modulation (PCM) systems, a frame is a set of consecutive time slots in which the position of each digit can be identified by reference to a frame-alignment signal. (This signal does not necessarily occur in each frame.) In a time-division multiplexing (TDM) system, a frame is a repetitive group of signals resulting from a single sampling of all channels. The term in-frame is used to indicate that a time-division multiplexer is properly synchronized with the demultiplexer on the other end of the link, so.
Electronic amplifier - this by taking power from a power supply and shaping the output to match the input signal. This process invariably introduces some noise and distortion into the signal, and the process cannot be 100% efficient - amplifiers will always produce some waste heat. An idealised amplifer can be said to be "a piece of wire with gain", the output is an exact replica of the input, only larger. Different designs of amplifier are used for different types of applications and signals. We can broadly divide amplifiers into three categories - small signal amplifiers, low frequency power amplifiers and RF power amplifiers. Each of these calls for a slightly different design approach, mainly because of the physical limitations of the components used to implement the amplifier, and the efficiencies that can be.
