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Electronics Engineering
Electronics Engineering is a branch of engineering that deals with practical applications of electronic components, devices, systems, or equipment. Electronics are devices that operate on low voltage sources, as in electron tubes, transistors, integrated circuits, and printed circuit boards and use electricity as part of its driving force.
24,372 Questions
We see LEDs every day. They're in lotsa stuff. A light-emitting diode (LED) is a semiconductor diodethat radiates light (electoluminescence) when current passes through it in the forward direction. Electrons move though semiconductor medium and "fall into" other energy levels during their transit of the p-n junction. When these electrons make a transition to a lower energy level, they give off a photon of light. This photon may be in the infrared region, or just about anywhere across the visible spectrum up to and into ultraviolet - but we have to pick a color when we make them. That means we can get an infrared LED to work in our remote controls, and get other ones of different colors to make indicators or, in large arrays, displays - even color ones. LEDs uaually are made to emit one color of light, though bicolor ones and more can be fabricated. Intensity is being improved as well. That broadens the applications considerably (think vehicular tail lights). The device has a pair of leads, and a (usually) plastic body moulded around the leads and the semiconductor crystal itself. That way the light can get out through the plastic. There is frequently a "round dome" at the top of the LED which serves to focus the light headed out through it. Remember that it is the material of the semiconductor crystal that determines the light given off by the device. A normal LED isn't really voltage dependent. When obtaining the LEDs, a manufacturer or hobbiest specifies the color. Red, green and blue are most popular, and, though there are other colors, it might be tough(er) to find them. Note that the big LED color displays use a three-LED pixel, and by driving it (the 3-LED assembly) appropriately, a wide range of colors can be obtained. This in an introduction to the LED. An electronics student will review semiconductor fundamentals and then more closely examine the chemisty and physics of the particular p-n junction that is fabricated to exhibit electroluminesce. A link is provided to the Wikipedia article on the light-emitting diode.
WHAT IS coherence bandwidth of radio channel?
The coherence bandwidth of a wireless channel is the range of frequencies that are allowed to pass through the channel without distortion.
The Javac is the java compiler javac.exe is a process associated with Java(TM) 2 Platform Standard Edition 5.0 Update 5 from Sun Microsystems, Inc.. Java Capusal this is a java compiler
What is a p plus type semiconductor?
This just means that the semiconductor has extra holes in it. On the order of 10^6 I believe.
How much voltage does a lead acid battery produce in an airplane?
A lead acid cell has an off charge/no load voltage of 2.2 volts, so that 12 cells in series will have a voltage of 26.4 volts. When you float this across a charging supply, standard practice is to increase the voltage to 2.3 volts per cell, so that the total voltage becomes 27.6 volts.
Airplanes normally have a 27.6 volt DC system, and larger aircraft also have a 115 volt 400 Hz system. Also, rare these days, possibly a 115 volt wild frequency system.
Note that the so called 12 volt system in a car is actually 13.8 volts.
Basic Call Services
- Provides functions of local office call, outgoing call and incoming call, and tandem of local call, special services, national toll call, international call, as well as function of automatic incoming call and outgoing call.
- Provides subscribers with service of direct dialing extensions of PBX or calling the manual desk of PBX.
- Extensions of PBX can dial out directly.
- Incoming trunk directly connected to the traffic console. Transferred by the attendant in BID mode (board inward dialing).
- Provides subscribers with various special call services, including various inquiries and declaration services (voice mailbox interface function has been provided).
- Provides subscribers with paging service or service of calling mobile subscribers.
- Can cooperate with connected Remote Switching Unit. If a PCM device between the Remote Switching Unit and home office is broken-down, self-switching shall be still workable for subscribers in the unit.
- Supports terminals such as coin phone, magcard phone, IC card or PBX with billing devices, and transfers called subscriber´s answer signal to these terminals.
- Can provide a subscriber with co-line but different numbers, and gives distinguishing ring according to the subscriber number.
- Supports PBX.
- Authentication function includes more than 8 types (includes: calling prefix, calling number, caller type, called prefix, called number, call attribute, call service right, outgoing/incoming trunk group identifier); the number analysis capability and store and forward capability could be 40 digits.
- Has the capability to recognize numbers of non-voice terminal such as data or facsimile, and ensures that it won´t be inserted by other calls or be forced to release.
- While tracing malicious call, if the calling line identification cannot be got, the incoming or outgoing trunk shall be checked.
- The toll call traffic console can insert local call subscriber or local call.
- During connection, if there are vacant number, number modification, temporary blocking, improper use or other recording performance, it can be connected automatically to the Announcement Recorder, no answer signals shall be sent. A vacant tone may be given for a vacant number.
- Announcement Recorder could be deployed, some special services like time report, can be provided to subscribers through voice recording.
- For PSTN subscribers, if a call is initiated in a local office, and the called subscriber´s on-hook signal is received, supervision shall be started immediately. The supervision time shall be 60s for a local call, 90s for a toll call and 120s for an international call. If the caller doesn´t on-hook to release the connection out of the supervision time, a busy tone shall be given to the caller. The tandem SPC switch transfers the called subscriber´s on-hook signal immediately once it receives it.
- While a subscriber dials a pre-defined special service number, the switch shall give ring after a short interval (0-3 seconds, could be set using man-machine commands).
- For automatic toll call connection, insertion or forced release can not be performed if the called subscriber is busy (local call busy or toll call busy); while toll call office or international attendant calls a local subscriber, if this subscriber is talking to another local subscriber, the toll call office or international attendant can send a ring signal automatically or the signal can be sent by attendant through pressing keys.
- While performing automatic or manual switchover in the data transmission system, if the transmission system is interrupted for no more than 6 seconds, the connection won´t be released; if the interruption lasts for more than 12 seconds, alarm must be given and the connection is allowed to be released.
- If the SPC switch receives "0" after an area code, the call won´t be connected so as to avoid confusion in routing and billing.
- While acting as call initiating home office, the SPC switch has the function to send out the calling line identification with or without an area code.
- Malicious call function. While the call is a malicious call, a line signal of malicious call shall be transmitted, and outgoing call control mode shall be modified.
- Trunk voice service.
- Man-machine commands to modify subscriber attributes.
- Newly added analog trunk unit to process corresponding analog trunk.
- Processing function of private network call service.
- Loop trunk.
- Supports KC15 function while selecting satellite circuit.
PSTN Featured Services
- Abbreviated Dialing
- Hot Line Service
- Outgoing Call Barring
- Don´t Disturb Service
- Malicious Call Tracing
- Alarm-Call Service
- Interception of Call
- Call Forwarding No Reply
- Call Forwarding Unconditional
- Call Forwarding On Busy
- Absent-Subscriber Service
- Call Back On Busy
- Call Waiting
- Three-Party Call Service
- Telephone Conference Service
- Calling Line Identification Presentation
- Calling Line Identification Restriction
- Office code restriction function: for any subscriber of the ZXJ10, maximum 96 office code numbers can be restricted. Namely, the subscriber can not dial out of these 96 numbers (positive restriction function) or the subscriber is only allowed to dial these 96 numbers (reverse restriction function).
- Report caller number function
- Tone detection function
- Busy release function, special service configuration. When a terminal is long time no response or is busy, a prompt tone shall be given or the call shall be transferred to another terminal to improve the connection rate. It is proved that this method can effectively release busy traffic.
- Arrearage subscriber control. By modifying the control indicators of arrearage subscribers, functions such as arrearage subscriber can call in, arrearage subscriber can not call in, no reply given, give arrearage tone, can be provided.
- Office code change, digit addition, and provision of prompt tone after the change and digit addition.
- Add statistics to incoming calls/outgoing calls to/from traffic console.
- Detection to the busy tone and dialing tone of some analog trunks in the loop.
- Addition or change to calling numbers. Total 4 modes to change calling number; Total 4 modes to change calling number.
- Whether the call can be transferred to toll call, and whether the incoming toll call can be forwarded.
- While attendant calls subscriber B, if B has activated call forwarding, do not disturb and absent services, arrearage or barring incoming calls, the attendant can override these services and call B directly.
- Data report and inquiry, provides maintenance personnel with more flexible means to inquire data.
- Man-machine commands in row format (including remote maintenance). These commands are added to maintain routine data and design the background/foreground of the database.
- Black/white list service. Call filtering can be performed through black/white list.
- Secretary service. If a subscriber activates this service, all calls for he can be connected firstly to another subscriber in the same Centrex group (the secretary), the secretary shall handle the calls or transfer the calls to him by using incoming call transferring function.
Why do LNB's have to be mounted close to the satellite dish?
The LNB takes the signal reflected off the dish, sends that signal through the coax cable to the receiver, where the receiver decodes the signal unlocking the channels you subscribe to.
Setting the low pass filter on a car sub woofer?
LPF setting: typically 60-100Hz. Most use ~80Hz. Depending on the sub and the type of music You listen to, if set too low the sub won't put out the wanted frequencies; to high and power is wasted on higher frequencies.
Cosmic rays are constantly coming down, coliding with the electrically charged atmosphere witch creates a massive ionization screening in the ionosphere. A giant world wide electromagnetic umbrella!
Norton's theorem is the current equivalent of Thevenin's theorem.
The experiments of Georg Ohm set the foundation for this law, which is also known as Ohm's Law.
A triac is a high voltage AC solid state relay it is switched on by applying a dc at the gate it can't be used to switch DC because it stay on while current is flowing even when the gate is low but with AC the current stop flowing when the cycle go zero and will switch of if the gate is low
A 30 volt 90 watt lamp has 3 amps going through it. The series resistor also has 3 amps going through it, by Kirchoff's current law. The voltage across the resistor is 90 volts. With 3 amps, that is 30 ohms. (By the way... The resistor must be rated to carry 270 watts. That is a lot of power for a resistor.)
Sources with different voltages should never be connected in parallel, you would have a difference of potential. Any time you have a difference of potential connected together you will have sparks, which could cause the batteries to explode.
What is rohani duniya email address?
WikiAnswers does not divulge private or personal information, such as telephone numbers, email addresses or home addresses, for individuals.
What is the difference between active and passive component?
Active means devices that perform functions in a non linear fashion [amplifiers] passive are components that perform according to a set of linear rules
An arbitrary identifying number. These numbers are usually selected by the first manufacturer of the part.
What happens if you connect one 8 ohm speaker to an amp rated 350w at 4 ohm?
No Problem to do this, but there are really no amplifiers with an output impedance of 4 ohms on the market. All loudspeaker amplifiers have an impedance of less than 0.5 ohm. Scroll down to related links and look at "Impedance bridging - Wikipedia".
Cells by mitosis and meiosis (;
What factors does the time constant of a thermocouple depend on?
It depends on the mass (m), specific heat (c), convective heat transfer coefficient (h) and the surface area (As)
In other words,
Time Constant = (m * c) / ( h * As)
When there is almost no resistance in a circuit what is it called?
This is what is known as a "short circuit".
Is yagi uda antenna have parasitic elements?
Yes, the Yagi-Uda antenna has several parasitic elements, in the form of a reflector ("behind" the driven element) and the directional elements ("in front" of the driven element).
What makes a AC freeze up at the coils after you have clean the coils and the AC has freon?
Bottom line: Start by checking the ducts and turning up the thermostat a few degrees. If you still have problems call a pro.
Reason:
The most common cause of icing on the evaporator coils is insufficient air flow. Check to make sure the ducts are clear of any obstructions or debris, particularly the inlet duct. Also make sure that you have not closed too many of your outlet registers.
If there is plenty of airflow but you are still getting icing, you are probably over-working the system. You may need to turn up your thermostat and deal with slightly warmer indoor temperatures until the weather cools off.
One final possibility, some systems have a hot gas bypass valve to prevent icing and if it is not functioning properly, that could be the culprit. I mention this last because it is not very common in home air-conditioners. If yours has one and it isn't working that would require professional assistance to diagnose and repair.
