DBS is a satellite technology that is used to spread both TV and radio programs and presently incorporates other services such as video-on-demand and interactive features. Nowadays DBS technology is utilized to broadcast television programs to any specific location from the definite position of the orbit. It covers both analog and digital signals and user requires relatively small dish antenna to receive signal from the satellite.
In digital service this technology used compression technique in order to accommodated more channels as well as ensure better sound and picture quality. In Germany free-to-air DBS service encompasses approximately 40 analogue and 100 digital channels broadcast from the SES Astra 1 position at 19.2 E it covers nearly 12 millions homes.
In United States commercial DBS service providers such as Direct TV and Dish Network have huge customer base and they used high power Ku band to deliver their services. India's national broadcaster, Doordarshan unveils their DBS service "DD Direct Plus" that includes their all DD channels and some radio channels.
All about Bluetooth
Bluetooth is the name for a short-range radio frequency (RF) technology that operates at 2.4 GHz and is capable of transmitting voice and data. The effective range of Bluetooth devices is 32 feet (10 meters). Bluetooth transfers data at the rate of 1 Mbps, which is from three to eight times the average speed of parallel and serial ports, respectively.
Bluetooth can be used to wirelessly synchronize and transfer data among devices. Bluetooth can be thought of as a cable replacement technology. Bluetooth can also be used to access a network or the Internet with a notebook computer by connecting wirelessly to a cellular phone.
Bluetooth is extremely secure in that it employs several layers of data encryption and user authentication measures. Bluetooth devices use a combination of the Personal Identification Number (PIN) and a Bluetooth address to identify other Bluetooth devices. Data encryption (i.e., 128-bit) can be used to further enhance the degree of Bluetooth security. The transmission scheme (FHSS) provides another level of security in itself. Instead of transmitting over one frequency within the 2.4 GHz band, Bluetooth radios use a fast frequency-hopping spread spectrum (FHSS) technique, allowing only synchronized receivers to access the transmitted data.
Edward Apurba Singha
(R) thedailystar.net 2007