Other Interface Standards

X.21 o    Eliminates most of control pins of EIA standards -Control signals are encoded to control characters -Send control characters within the data line -More control information for digital telephony o    For digital communication between devices over a network, rather than just between DTE and DCE o    DB-15, Work with balanced circuits at 64Kbps ™   MODEMS o    Most familiar type of a DCE o    We require modem to connect to the internet o    MODEM is a composite word for modulator and Demodulator o    Modulator converts a digital signal into an analog signal using ASK, FSK, PSK or QAM o    A demodulator converts an analog signal into a digital signal o    While  a  demodulator  resembles  an  analog-to-digital  converter,  it  is  not infact a converter of any kind o    It does not sample the signal to create a digital signal o    It just reverses the process of modulation that is it performs demodulation o    Shows the relationship of a modulator with a demodulator o    Two PCs at the end are DTEs, and the modems are the DCEs