Development

Over time, the development of modem technology is constantly increasing use of the simplest modulation technique to the advanced modulation techniques. The journey begins with the emergence of the history of modem speed modem 300 bps and then continued to increase up to 56.4 Kbps.

a. 300-bps modem. The protocols were first used in this modem is a Bell 103 and V.21 can send up to 300 bps with modulation technique PSK (Phase Sift Keying).

b. 2400 bps modem. The modem is using V.26 or V.22 bis protocol, with PSK or QAM modulation techniques. Speed ​​was achieved at 2400 bps to 1200 bps fallback rate.That is, if the channels used do not meet the requirements to reach speeds of 2400 bps, then kecepetannya will be automatically reduced to 1,200 bps.

c. 4800 bps modem. Dipergunakannya V.27 protocols with PSK modulation technique. Speed ​​was achieved at 4800 bps to 2400 bps fallback rate.

d. 9600 bps modem. The protocol used in this modem V.29 with QAM modulation technique. Speed ​​that can reach 9600 bps with fallback rate 7200 or 4800 bps.

e. 14,400 bps modem. These modems use the V.33 protocol with the modulation technique TCM (Trellis coded modulation). Speed ​​that can reach 14,400 bps with fallback rate is 12,000 bps.

f. 19,200 bps modem. It uses the V.34 protocol with TCM modulation technique.Speed ​​that can reach 19,200 bps with fallback rate is 14,400 bps, 12,000 bps and 9600 bps.

g. 28,800 bps modem. Protocols using the V.34 modulation technique with TCM.Speed ​​reaches 28 800 14 400 bps bps with fallback rate.

h. 33,600 bps modem. The protocol used by V.34 modulation technique of TCM.Speed ​​that can reach 33,600 bps with fallback rate and 19,200 bps.

j. 56 Kbps modem
Modem technology continues to grow and for now there are several modem manufacturers that have successfully created the latest generation of modems with speeds of 56 Kbps modem, but as happened in previous generations, this modem can not reach speeds of 56 Kbps when installed PSTN network.
But there are several factors that cause the user can never reach speeds of 56 Kbps, among others:
1. The lack of compatibility (compatibility) between the technologies used in modem with modem
pool.
2. PSTN network performance is less good in the physical sense as well as from density data communication pull through it.
3. The use of technologically ADC (Analog to Digital Converter) which caused the noise quantisasi, which can reduce transmission speed modem.
Based on the technology used, 56-kbps modems are divided into two types, namely x2 technology and K 56 Flex.

Source : Suara Merdeka