Subject: audio video system Branch: electronics &communication

Presentation on : CATV Prepaired by : 130940111010

CATV Cable television systems referred to as community antenna television(CATV). This started to provide signals in areas that where in shadow region or those who did not received signals from broadcast station.

CATV can encompass large areas as there is no restriction of channel allocation. A cable converter box can give the selection of channels. Fig. shows a typical CATV network.

Typical cable television system has: Head end : Which is the central origination point of all signals carried. Trunk system : That carries signals to everyone.

Distribution system : Which is bridged from system the trunk system and carries signals into subscriber’s home. Subscriber drop : Individual line to subscriber’s receiver fed from taps in the disribution system.

Head end Broadcast signals are picked up They are amplified and fed into trunk lines UHF channels are converted to VHF and local studio signals are also added As usual video and audio signals modulate separate carriers

Trunk amplifiers in trunk system There are at least 30 trunk amplifiers in a line at regular intervals to keep the signals at a standard level. A typical bridging amplifier has a gain of about 20 dBs. The output of this amplifier is for the branch lines to individual subscribers.

Distribution system This has line amplifiers. Line extender amplifiers are inserted in the branch line to make up for the cable losses that connects the distribution system. The trunk line must not get loaded by the connection of all branches. The signal power taken from the trunk must be kept small.

A directional coupler with three terminals is normally used A directional coupler with three terminals is normally used. One for input,other one to carry signal through trunk line and third tapped one for individual branches. The final tap on the system is to subscriber’s home connected with coaxial cable connector.