The acronym for CNC is Computer Numerically  Controled. A control system in which numerical values corresponding to desired tool or control positions are generated by a computer. Abbreviated CNC. Also known as computational numerical control; soft-wired numerical control; stored-program numerical control.

Computer numerical control(CNC):

The method of controlling machines by the application of digital electronic computers and circuitry. Machine movements that are controlled by cams, gears, levers, or screws in conventional machines are directed by computers and digital circuitry in computer numerical control (CNC) machines.

Computer numerical control (CNC)provides very flexible and versatile control over machine tools. Most machining operations require that a cutting tool be fed at some speed against a workpiece. In a conventional machine such as a turret lathe, the turning tool is mounted on a slide with hand-operated infeed and crossfeed slides. The operator manually turns a crank that feeds the cutting tool into the workpiece (infeed) to the desired diameter. Another crank then moves the turning tool along the longitudinal axis of the machine and produces a cylindrical cut along the workpiece. The feed rate of the turning tool is sometimes controlled by selecting feed gears. These gears move the axis slide at the desired feed. A CNC machine replaces the hand cranks and feed gears with servomotor systems.

Computer numerical controls(CNC) allow the desired cut depths and feed rates to be “dialed in” rather than controlled by cranks, cams, and gears. This provides precise, repeatable machine movements that can be programmed for optimal speeds, feeds, and machine cycles. All cutting-tool applications, whether on a lathe, drill press, or machining center, have optimum speeds and feeds, which are determined by carefully weighing the economics of tool life, required production rates, and operator attentiveness. With computer numerical control these parameters are set once, and then they are repeated precisely for each subsequent machine cycle.

In computer-aided manufacturing (CAM), computers are used to assist in programming CNC machines. In sophisticated CNC manufacturing operations, machined parts are first designed on computer-aided-design (CAD) equipment. The same electronic drawing is then used to create the CNC part program automatically. A less advanced version of CAM is the use of high-level part programming languages to write part programs

Computer numerical control machines are used mainly when flexibility is required or variable and complex part geometries must be created. They are used to produce parts in lot sizes of a few pieces to several thousand. Extremely large manufacturing lot sizes frequently call for more product-specific machines, which can be optimized for large production runs.

What is GSM ?

GSM - Global System for Mobile Communications is the most popular standard for mobile telephony systems in the world.

What is a GSM Modem?

A GSM modem is a wireless modem that works with a GSM wireless network. A wireless modem behaves like a dial-up modem. The main difference between them is that a dial-up modem sends and receives data through a fixed telephone line while a wireless modem sends and receives data through radio waves.

A GSM modem can be an external device or a PC Card / PCMCIA Card. Typically, an external GSM modem is connected to a computer through a serial cable or a USB cable. A GSM modem in the form of a PC Card / PCMCIA Card is designed for use with a laptop computer. It should be inserted into one of the PC Card / PCMCIA Card slots of a laptop computer.

Like a GSM mobile phone, a GSM modem requires a SIM card from a wireless carrier in order to operate.

As mentioned in earlier sections of this SMS tutorial, computers use AT commands to control modems. Both GSM modems and dial-up modems support a common set of standard AT commands. You can use a GSM modem just like a dial-up modem.

In addition to the standard AT commands, GSM modems support an extended set of AT commands. These extended AT commands are defined in the GSM standards. With the extended AT commands, you can do things like:

* Reading, writing and deleting SMS messages.

* Sending SMS messages.

* Monitoring the signal strength.

* Monitoring the charging status and charge level of the battery.

* Reading, writing and searching phone book entries.

The number of SMS messages that can be processed by a GSM modem per minute is very low — only about six to ten SMS messages per minute.

What is a GPRS Modem?

A GPRS modem is a GSM modem that additionally supports the GPRS technology for data transmission. GPRS stands for General Packet Radio Service. It is a packet-switched technology that is an extension of GSM. (GSM is a circuit-switched technology.) A key advantage of GPRS over GSM is that GPRS has a higher data transmission speed.

GPRS can be used as the bearer of SMS. If SMS over GPRS is used, an SMS transmission speed of about 30 SMS messages per minute may be achieved. This is much faster than using the ordinary SMS over GSM, whose SMS transmission speed is about 6 to 10 SMS messages per minute. A GPRS modem is needed to send and receive SMS over GPRS. Note that some wireless carriers do not support the sending and receiving of SMS over GPRS.

If you need to send or receive MMS messages, a GPRS modem is typically needed.

Which is Better: Mobile Phone or GSM / GPRS Modem?

In general, a GSM/GPRS modem is recommended for use with a computer to send and receive messages. This is because some mobile phones have certain limitations comparing to GSM/GPRS modems. Some of the limitations are described below:

Some mobile phone models (example: Ericsson R380) cannot be used with a computer to receive concatenated SMS messages.

What is a concatenated SMS message?

A concatenated SMS message is a message that contains more than 140 bytes. (A normal SMS message can only contain at most 140 bytes.) Concatenated SMS works like this: the sender’s mobile device breaks a message longer than 140 bytes into smaller parts. Each of these parts are then fitted in a single SMS message and sent to the recipient. When these SMS messages reach the destination, the recipient’s mobile device will combine them back to one message.

What is the cause of the problem?

When the mobile phone receives the SMS messages that are parts of a concatenated SMS message, it combines them to one message automatically. The correct behavior should be: when the mobile phone receives the SMS messages that are parts of a concatenated SMS message, it forwards them to the computer without combining them.

Many mobile phone models cannot be used with a computer to receive MMS messages. Because when they receive a MMS notification, they handle it automatically instead of forwarding it to the computer.

A mobile phone may not support some AT commands, command parameters and parameter values. For example, some mobile phones do not support the sending and receiving of SMS messages in text mode. So, the AT command “AT+CMGF=1″ (it instructs the mobile phone to use text mode) will cause an error message to be returned. Usually GSM/GPRS modems support a more complete set of AT commands than mobile phones.

Most SMS messaging applications have to be available 24 hours a day. (For example, an SMS messaging application that provides ringtone downloading service should be running all the time so that a user can download ringtones any time he/she wants.) If such SMS messaging applications use mobile phones to send and receive SMS messages, the mobile phones have to be switched on all the time. However, some mobile phone models cannot operate with the battery removed even when an AC adaptor is connected, which means the battery will be charged 24 hours a day.

Besides the above issues, mobile phones and GSM/GPRS modems are more or less the same for sending and receiving SMS messages from a computer. Actually, you can consider an AT-command-enabled mobile phone as “GSM/GPRS modem + keypad + display + …”.

There is not much difference between mobile phones and GSM/GPRS modems in terms of SMS transmission rate, since the determining factor for the SMS transmission rate is the wireless network.

Despite your efforts, it is quite likely that you may not be satisfied with your performance. Why is this so? Of a host of reasons, they way we study is an important one. You need to meet a few basic study requirements, if you intend to get the maximum from learning at a distance.

Let us be clear that there are no shortcuts to do well in studies. However, with good study habits, you can study better.

Motivation is the single most important factor for studying well. You choose to study a Programme at a distance, because you feel that a successful completion of this Programme will help you in social mobility. In other words, you have joined the Programme by choice and not by chance. Motivation, in your case, therefore, is not a problem. But, sustaining the motivation may at times pose problems, especially when you study in isolation. You should be aware of it.

• Keep you mind open to new, perhaps, conflicting ideas and experiences. At times, you will come across topics/issues in the Course, which may not have been dealt with the way you want them to be. Now, try to understand the viewpoint of the writer. There may be some purpose for the writer to present them so. Or, the writer may be wrong. If the latter is the case, write to the person concerned or the institution concerned and express your concerns. This is important, as most often we develop an aversion to the subject just because we don’t like the teacher! We know that it is very east to say, “have a positive attitude”, but not so easy to imbibe. But, without a positive attitude you will contribute to making things harder for yourself.
• Look for principles and the basic unifying ideas in the subject. Usually, exemplary students are those who can see a Course as a ‘whole’ and not in its parts. It is true that we usually read sequentially (say from Unit 1 to 2, 3 and then to 4 and so on.) Looking at the Course as a ‘whole’, on the other hand, means to find the common thread of argument across the Units. In other words, analytical reading should lead you to synthesize what you have read. This helps in more fully understanding the subject.
• Set clear and realistic goals. Even with a positive attitude, you will at times face difficulties as a distance learner. Many students have expectations, which are very high and are disappointed when they cannot meet them. If our expectations of ourselves are too high, we will become stressed and will be unable to complete even simple tasks. In fact, we will make sure that we cannot succeed! However, without goals you will not be able to plan your life. Take a moment to think about your own goals for your study. Think about short-term goals (say, over the next few days/weeks/months) and long-term goals (over the next few years). Write these down. For example:
• long-term goal: to enroll for a Programme in (specify year), to get a Master’s degree in (specify year), to do one subject which will require approximately 15 hours for study per week over a period of 13 years.
• short-term goal: to spend 15 hours of time on my studies every week (starting from…), to study for 2 hours on Monday, 1 hour on Tuesday, 3 hours on…and so on.
• work to a plan, plan what you want to achieve in the next day, week…,
• tick to your plans, or modify them for good reasons only,
• put to use, in the best possible way, every bit of time available,
• understand that one who plans will get ample time to have rest,
• realize that you will have to sacrifice something in order to find time for the Programme.

Get support from the dear ones. Besides being a distance student, you no doubt have many social roles to play – that of a spouse, parent, friend, employee and so on. When you first return to studies, it can be a difficult time for the ones around you. Hopefully, you have envisaged it. If not, now try to discuss with them reallocation of duties and responsibilities, etc. After all, people who are around us do matter.

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