Modems:

• Modems perform two main functions:  Modulation / Demodulation
• Analog signal vs Digital
• Modulation: converts digital to analog
• Demodulate: analog to digital

Common Modem types:

• Cable modem
• ADSL (asymmetric digital subscriber line)  downstream faster then upstream  (SDSL)  symmetrical…..
• DSL (digital subscriber line)

Wireless Access Points:

• device that allows wireless devices to connect to a wired network using Wi-Fi, or related standards
• Wireless Access point vs ad Hoc
• Range of frequency (obsticals)
• Can on send or receive (half duplex)   so 802.11g = 54Mbps really is only 25Mbps
• 2.4 GHz  or 5 Ghz
• 802.11n = 300Mbps
• 802.11ac = 450 Mbps /  1300Mbps 5 Ghz

CSU / DSU

A CSU/DSU (Channel Service Unit/Data Service Unit) is a digital-interface device used to connect a Data Terminal Equipment device or DTE, such as a router, to a digital circuit, such as a T1 line. The CSU/DSU implements two different functions. The CSU is responsible for the connection to the telecom network while the DSU is responsible for handling the interface with the DTE