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A: Ampere. A flux of electrons that amounts to 1 Coulomb per second. Coulomb is a certain constant amount of electrons (quantum particles).
AC: Alternating Current. A current that changes direction (sign) over time. Also used for describing votlage etc. that is alternating.
Allen head
Ampere: See "A".
Amplification factor: How many times BJT’s output current is bigger than it’s input current. Ratio between output and input current.
AUI: Attachment Unit Interface. An interface on 10Mbps NICs that looks exactly like gameport, only instead of screw fasteners there is a sliding latch. This interface is designed for connecting various external transceiver units.
BJT: Bipolar Junction Transistor. A classical transistor. First transistors were BJT.
Carrier beam: Light beam that is modulated and carries data by this modulation.
Cheese head
Coaxial cable: A center (live) insulated wire wrapped into conductive tube or fabric or foil (ground). In ideal case it doesn’t leak any signal out.
dB: Decibel. 1/10 of bel. 0 bels is 1:1 power ration, 1 bel is 10:1 power ratio, 2 bels are 100:1 power ratio, 3 bels are 1000:1 power ratio, -1 bel is 1:10 power ratio etc. And decibel is simply 1/10 of bel. so that number_of_decibels=10*log_10(measured_power/reference_power).
DC: Direct Current. A current that flows still in the same direction. Also used for describing voltage etc. that is steady.
Differential Limitter: A pair of bipolar transistors connected by their emitters that is immune to input overdrive and limits (clips) the output at certain amplitude without sticking that normally occurs by flooding the transistor junction with charge carriers.
Digital Multimeter: Usually a 3 1/2 digit (max. readout 1999) digital meter that knows how to measure AC/DC voltage, current, resistance, transistor amplification, diode forward voltage etc.
EIRP: Equivalent Isotropic Radiator Power. The power an isotropic radiator would have to appear equally strong from the direction of strongest radiation of the measured device.
EMC: ElectroMagnetic Compatibility. That the device is able to run without any problems even under attack of strong electromagnetic waves from outside.
DPDT: See "Switch"
EMI: ElectroMagnetic Interference. These are generally issues about making devices that radiate only negligible amount of energy in electromagnetic waves.
FET: Field Effect Transistor. Transistor architecture. The flow of current is regulated by strangling the conductive channel in the semiconductor by external electrical field influence without injecting any control current into the semicinductor channel itself. Suffers from thermal noise less than from quantum noise. FET behaves exactly like a tube (valve, lamp). Even the equations that describe them are the same. :)
Fiberless Optics: The same as FSO.
FSO: Free Space Optics. Transmitting data over a distance by light beam without physical carrier medium (in plain air or in space).
Ground: An electric reference point. In Ronja electronics it is the metal case.
Hex head
Hz: Hertz. Means one revolution (cycle) per second. A measure of frequency of time periodical phenomena.
Infrared: Light that has a bit too low frequency to be seen, so is off the red end of visible spectrum. Produced by Sun in almost as large quantities as normal light, too.
Isotropic Radiator: A radiator that radiates in all directions with the same strength.
JFET: Juction FET. A FET where insulation between gate and channel is done by reverse-biased diode junction.
LED: Light Emitting Diode.
mApp: Milliamper peak-to-peak. Peak to peak means measured from the highest value occuring in the wave to the lowest one.
MAU: Media Attachment Unit. The transceiver itself (IEEE 802.3 terminology).
MOS: Metal-Oxide-Semiconductor. A transistor architecture. Used in the first stage of Ronja for it’s excellent noise performance. Has more thermal noise and less shot (quantum) noise.
MOS Tetrode: A solid-state quivalent of tetrode tube (lamp). Also called cascode. Two triodes one atop another. The lower one converts input voltage into current. The top one converts the current into voltage. This is because it doesn’t suffer from Miller effect. The output wire is not connected with the input one by juction capacitance (so called reverse transfer capacitance) and thus can’t feedback the output signal into the input and thus drastically reduce the amplification factor.
mVpp: Millivolt peak-to-peak. Peak to peak means measured from the highest voltage occuring in the wave to the lowest one.
NIC: Network Interface Card, also Network Card.
Nominal Maximum Distance: The device normally works longer than this distance in clear weather, but it is forbidden in the specification to use the device on longer distance than Nominal Maximum, because it would mean problems in common weather where various hazes, sunshine into the receiver or fogs and mists exist. This distance is estimated, so that the dropouts still don’t annoy the user. The dropouts will always be there because theoretical calculations show that practical (even very expensive) systems are limited to 500m of distance if we required a 100% availability.
PCB: Printed circuit boards. A board with copper traces for electronic circuit.
Philips head
Photodiode: A device on which photon (a piece of light) falls and an electron (a piece of electricity) falls out.
PIN: Positive-Intrinsic-Negative structured photodiode. An extra-fast photodiode.
RSSI: Received Signal Strength Indicator. A wire going from the receiver where the voltage increases as received signal strength increased.
RTT: Round Trip Time. A time the message spends travelling around the loop (to and from).
RX: Receiver.
Shielding: Wrapping something into a very good conductor to make a barrier for electromagnetic waves. Electromagnetic waves are being reflected by conductors. If they are good enough (i. e., thick foil, as tiny holes as possible, good contact all the way around all seams) they reflect the waves totally like a metal surface reflects light and heat radiation. So no waves can get from outside to inside and vice versa.
Shot Noise: A noise generated where quantum particle (electrons, photons) impinge somewhere and get detected. The noise is caused by randomness of their arrival times. An arrival of a single particle generates Dirac impulse which has a character of white noise. If the arrivals are uncorrelated then the Dirac impulses add up without phase distortion and a shot noise occurs. This noise occurs by DC illumination of the receiver photodiode and is one of main limitting factors of FSO systems. Also occurs in diodes where quantum particles (electrons) fall over a potential barrier (0.7V for Si).
The noise current received in band of witdh B [Hz] is 2eBI, where e is a charge of elctrons and I is the DC current that causes the noise.
Stereo image: Image consisting of two nearly identical images one aside the other that compose 3D virtual image in your brain. Stereo images in Ronja project are photographed for convergent (aka crosseye) viewing. See Stereo Viewing tutorial. (Ignore the information about RasMol.)
Switch: Switch is a device that makes contact between two wires and breaks it back apart. Everyone probably knows that. But the taxonomy is not trivial. See explanation of switches.
SPDT: See "Switch"
STP: Shielded Twisted Pair. See also "TP".
Thermal noise: A noise generated by movement of electrons of certain temperature in a resistor. The electrons are being kicked around by the vibrating atoms and generate noise spectral power density on the terminals of the resistor. The power received in a bandwidth B [Hz] at temperature T [Kelvins] is BkT, where k is Boltzmann’s constant. Is not generated by coils and inductors because the matter of these components doesn’t interact with the electrons (has no resistance) and thus can’t kick them around.
Thermal noise comes into play in the night, when the quantum noise from Sun’s DC irradiance gets quiet. Sources of thermal noise in FSO devices are resistance of the power feed resistor for the RX PIN diode and channel equivalent noise resistance (about 4/3 of forward transfer admittance) of the input MOSFET tetrode.
Transmitter diode: A LED with high output that is used for transmitting the carrier beam.
TP: Twisted Pair. Common NIC interface that uses a pair of wires twisted together. Twisted pair doesn’t leak the signal much but from principle always leaks signal, even in ideal case (infinitely conductive wire, infinitely symmetrical).
Transceiver: A device that is able to perform both functions of receiver and transmitter (not necessarily at the same time).
TX: Transmtiter.
Twisted Pair: See "TP".
UTP: Unshielded Twisted Pair. See "TP".
V: Volt. Unit of electrical potential (voltage). Electrical voltage is a measure how much work it takes to move an electron along a certain (examined) path. Where the field is not much wild, the path itself doesn’t matter, just the endpoints.
Video Amplifier: A bunch of transistors optimized for stable wideband amplification. Was used in video circuits, hence the term Video Amplifier.
Volt: See "V".
Wireless Optics: The same as FSO.

Glossary

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