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In a digitally modulated signal or a line code, symbol rate, modulation rate or baud rate is the number of symbol changes, waveform changes, or signaling events across the transmission medium per unit of time. The symbol rate is measured in baud (Bd) or symbols per second. In the case of a line code, the symbol rate is the pulse rate in pulses ...
Since most such codes correct only bit-flips, but not bit-insertions or bit-deletions, the Hamming distance metric is the appropriate way to measure the number of bit errors. Many FEC coders also continuously measure the current BER.
As the description implies, is the signal energy associated with each user data bit; it is equal to the signal power divided by the user bit rate (not the channel symbol rate). If signal power is in watts and bit rate is in bits per second, E b {\displaystyle E_{b}} is in units of joules (watt-seconds).
Wireless devices, BPL, and modems may produce a higher line rate or gross bit rate, due to error-correcting codes and other physical layer overhead. It is extremely common for throughput to be far less than half of theoretical maximum, though the more recent technologies (notably BPL) employ preemptive spectrum analysis to avoid this and so ...
When UI is used as a measurement unit of a time interval, the resulting measure of such time interval is dimensionless. It expresses the time interval in terms of UI. Very often, but not always, the UI coincides with the bit time, i.e. with the time interval taken to transmit one bit (binary information digit).
This model of the Apple keyboard also has two down-stream USB 2.0 ports, one at each end of the keyboard (like M2452 and M7803). This model was renamed as the 'Apple Keyboard with Numeric Keypad' after the release of the A1242 model in March 2009. This model was discontinued on 5 June 2017 and was the last wired keyboard produced by Apple. [26]
2 October 2008 July 2011 Mac mini (Early 2009) 2.00–2.66 1066 3 1 2 March 2009 July 2011 Mac mini Server (Late 2009) 2.53–2.66 1066 3 1 2 October 2009 July 2011 Core 2 Duo ("Wolfdale") iMac (Late 2009) 3.06–3.33 1066–1333 3–6 1 2 October 2009 July 2010 Core 2 Duo CULV ("Penryn") MacBook Air (Late 2010) 1.40–1.60 800 3 1 2 October 2010
(A1843) Magic Keyboard with Numeric Keypad, [2] first available in June 2017; This keyboard's design was similar to its predecessor, but had a lower profile. Apple re-engineered the scissor mechanism to increase key stability by 33 percent and reduce key travel. Typeface on the keys was also changed, from VAG Rounded to San Francisco (SF Compact).