Day 15 - Cathode Ray Tube

Description

Cathode Ray Tube (CRT) is a vacuum tube that contains electron gun to beam and display images on a phosphorescent screen. The images is displayed on screen by using technology called rastering. (The image displayed line by line in fixed pattern) CRT were used to as a display monitor in older times and now were completely obsolete and replaced by newer Plasma and LCD monitor technology.

CRT display monitors usually very thick and heavy due to the internal construction. The screen must be coated with a lead glass to block off any X-ray emission.

Advantages

- No native resolution
- No input lag
- High contrast ratio
- Works with light guns
- Longer shelf time
- Can store in extreme temperature without degrading the monitor

Disadvantages

- Heavy and bulky
- Higher power consumption rate
- Very dangerous to repair
- Contains poisonous material such as lead
- Sensitive to magnetic interference

This article is referred from Wikipedia's Cathode Ray Tube article.

Day 14 - Universal Serial Bus (Part 2)

Types

There are 3 types of connectors, A, B and C.

Type-A

Probably the most common one of all three. It is used on almost all flash drives, power adapters, accessories and even speaker. It shape is rectangular and backward compatible for all versions. There are also mini-A and micro-A USB, but peripherals that uses this standard is very rare.

Type-B

USB Type B is less common. It is more squared compared to other types. It is usually used on printers and scanners. 3.0 ports supports backward compatible, but the 3.0 connector won't work in 2.0 port. It also has two smaller versions called mini-B and micro-B, which people can use it to charge small electrical appliances and older phones.

From left to right: Standard-B, Mini-B, Micro-B, Micro-B USB 3.0 and Standard-B USB 3.0.

Standard-B is used to connect large peripherals such as printers or scanners. Mini-B use to connect older portable devices while micro-B use to connect latest portable devices. The 3.0 versions of standard-B and micro-B are just upgraded to a faster speed.

Type-C

USB Type C is the latest standard. It is rarely used on a computer but more to mobile devices for chargers. USB Type C is tiny as it is only one third of an USB Type A. The feature that is most noticeable for Type C is that it do not have specified orientation, so user can plug it without worrying the USB is plugged upside-down.

This article is referred from Wikipedia's USB article.

Day 13 - Universal Serial Bus (Part 1)

Description

Universal Serial Bus (USB) is a standardized connector that replaced a lot of other older connectors such as PS/2. Game Port and Parallel Port. It provides connection and data transferring, as well as power supply to portable devices.

Version

Different version have different transfer speed. It is easy to determine the version of the USB by looking at the color code on the connecter. Blue color coded USB are usually 3.0 or 3.1 while other colors are usually below 3.0. Also, USB 3.0 or above should have the word SS in front of the logo to represent Super Speed.

Speed

The speed of USB is determined by it's respective versions. There are 4 major versions which is 1.0, 2.0, 3.0 and 3.1.

There are two types of USB version 1.0 which is Low Speed (1.5 Mbit/s) and Full Speed (12 Mbit/s). 2.0 brings High Speed delivering 480 Mbit/s of data transfer. Version 3.0 speed is 10 times faster (5 Gbit/s, SuperSpeed) than version 2.0 and version 3.1 is twice as fast as version 3.0 (10 Gbit/s, SuperSpeed+)

This article is referred from Wikipedia's USB article.

Day 12 - Simplex, Full Duplex and Half Duplex

Description

Simplex means the information is sent one way only, usually from the sender A to receiver B and cannot be switched back. Duplex means the information can be send both way, from A to B or B to A, or both at the same time.

The word simplex might be derived from 'Sim' which means 'Simple' and 'plex' which means 'Part of' or 'Structure'. The word duplex is derived from 'Du' which means 'Duo' and 'plex' which means 'Part of' or 'Structure'.

Simplex

Simplex sends the information one way only and the path is fixed. Examples are TV and radio broadcasting, where the receiver only receive but not send information.

Full Duplex

In full duplex, both parties can communicate simultaneously. Telephone is a type of full duplex communication tool, as both parties can be both sender and receiver (To speak and heard at the same time).

Half Duplex

Half duplex the other hand allows information to flow both way, but not simultaneously, which is, one party is the sender while another must be the receiver. Walkie-talkie is a half duplex communication tool, as a talker will push a button called 'Push-to-talk' to turn off the receiver but turn on the transmitter.

This article is referred from Wikipedia's Simplex communication and Duplex (telecommunications) article.

Day 11 - Modem (Part 2)

Types of modem

There are 4 types of modem, which is Internal modem, External modem, On-board modem and Removable modem.

Internal modem are the modem that is NOT on a motherboard itself, but it is connected to a connector (Usually PCI slot). These modem can be called as network card. External modem are the modem between computer and the Internet. They usually contained in a box and connected using cables, usually serial or USB.

On-board modem is the modem located on motherboard itself. It cannot be removed but can be disabled when needed. Removable modem are wireless network cards connected through USB or older serial ports. It can be removed.

Versions of modem

Modem are classified by the rate of data transfer in a certain amount of time. They also classified by symbol rate (Baud) and connection method. Two main version are Digital Subscriber Line (DSL) and Dial-up.

DSL modem are very common to transfer data using the telephone line. There are a few types of DSL modem, but most of them are Asymmetric Digital Subscriber Line (ADSL). ADSL has different speed for uplink and downlink, that is, download speed is usually faster than upload speed. 

An uncommon modem called Symmetric Digital Subscriber Line (SDSL) allow the speed to be similar on both download and upload. Very highspeed Digital Subscriber Line (VDSL) divides the telephony line and data line into two band, so telephony line won't interfere with data line, thus improving the speed.

Other than DSL, another type of modem called Dial-up is an older way of connecting to the Internet. User are required to use the dial the phone number of an Internet Service Provided (ISP) to connect to the Internet. This kind of connection method is not widely used but it is very common for the 90s as the speed is slower than other connection method.

This article is referred from Wikipedia's Modem article.

Day 10 - Modem (Part 1)

Description

Modem is the short for Modulator and Demodulator. It is a hardware that use to communicate with other distant computers or more commonly used to connect to the Internet nowadays. 2 modems are required to make a connection and each modem can send and receive data.

Modulation and Demodulation

Modulation is an act of encoding the digital data from a computer into analog signal. Demodulation is an act of decoding the analog signal back to digital data.

This article is referred from Wikipedia's Modem article.

Day 9 - Open Systems Interconnection model

Description

Open Systems Interconnection or OSI for short, is a conceptual network model that standardize the communication function in a system. The goal is to intercorporate all communication systems into one model using standard protocol. This model is very similar to the networking model of TCP/IP but the difference here is it has 7 layers instead of 4 in TCP/IP.

Layer 1: Physical Layer

It mostly deal with raw data. The data is transported using electrical impulse, light or radio wave physically. It also define the transmission mode and the use of network topology. Ethernet is one of the physical layer entity.

Layer 2: Data Link Layer

Data are encoded and decoded into bits here. It also contains Media Access Control (MAC) and Logic Link Control (LLC). MAC handles the network access permission while LLC handles the flow control and do error checking. Point-to-Point-Protocol is one of the data link layer entity.

Layer 3: Network Layer

Everything about network are handled here. Packet switching (Switch from a message to several packets), routing of packets and virtual circuit for node to node networking can be found here. Other features such as addressing, error handling and congestion control works together here. Internet Protocol is one of the network layer entity.

Layer 4: Transport Layer

This is the layer that manages where to flow the datagram and avoid possible congestion. It also detect datagram error. Transmission Control Protocol (TCP) is one of the transport layer entity.

Layer 5: Session Layer

This layer manage the connection between application. For example, session layer can establish a
connection if the connection is lost. Remote Procedure Calls (RPC) is one of the session layer entity.

Layer 6: Presentation Layer

Presentation layer translate normal text from application to network format and vice versa. This layer will change the data format and encrypt it. Encryption is one of the presentation layer entity.

Layer 7: Application Layer

This layer can interact with users directly. This layer provides mailing services, file transfer and Internet browsing. File Transfer Protocol (FTP) is one of the application layer entity.

This article is referred from Wikipedia's OSI model article. (With a few sub-articles)