Dial-up Modem basics and manufacturers
Modem is the short form of modulator-demodulator. Dial-up modem is used to establish internet connection using existing plain old telephone exchange via telephone line in the house or office premises, the same is depicted in the figure below. Dial up modem will have two ports one is voice port where telephone line is connected and the other one is data port where PC is connected.
It provides low data rate connection out of all the modem technologies available but require less investment if one has analog telephone line in the premise. The disadvantage of dial up internet is if one uses internet the same telephone line cannot be used for making voice calls or receiving voice calls.
ITU-T or CCITT has classified various standards based on data rate/modulation type the dial up modem supports. They are called as V series of standards. Few of them are summarized below.
Dial-up modem converts digital data into analog form compatible to be transported via analog telephone line.
ITU V.21 - Audio FSK, 300 bps
ITU V.22 - PSK, 1200 bps
V.32 -9600 bps
V.34 -28.8Kbps and 33.6kbps options, backward compatible with V.32
V.92 -Transmit at same speed of V.90 with some more features
PPP (point to point protocol) is used in dial-up modem to establish connection with ISP's server.
It has more features compare to its predecessor SLIP (Serial Line Internet protocol). PPP is defined in RFC 1661.
PPP is regarded as data link layer protocol and is interfaced with network layer of the system to establish the TCPIP connection with peer entity.
Dial up modem manufacturers
Following table mentions dial up modem manufacturers:
|Conexant, Website: www.conexant.com|
|Zoom Telephonics, www.zoomtel.com|
Refer our page on HF radio Modem or High Frequency radio modem Manufacturers/Suppliers.
Refer our page on GSM Modem/GPRS Modem Manufacturers/Suppliers.
Refer our page on Satellite Modem Manufacturers/Suppliers.
Refer our page on dsl Modem basics and manufacturer of dsl modem.
Refer our page on cable modem basics and manufacturer of cable modem.