Digital Terrestrial Television
Cable AML is a leading provider of integrated DTT (Digital Terrestrial Television) Systems. The company can provide systems in any of the formats adopted in the Western Hemisphere: ATSC (Mexico, Central and North America), DVB-T & T2 (Europe, Africa and Middle East) and ISDB-T/TB (several countries in South America).
A TDT system includes as a minimum the Digital Headend, the Transmitter and the Antenna with their accessories. Many systems also incorporate Repeaters (to improve coverage area of the main transmitter) and STL Microwave Links (transmission links from the studio to the transmitter).
The DVB-T / T2 systems can also include encryption equipment.
If the programs are transmitted “in the open” (without encryption) the customer can connect the TV Set directly to the antenna. However, the TV programs can be encrypted with a CAS (Conditional Access System), in which case the customer must use a Set Top Box between the antenna and the TV Set to decipher those signals that are authorized for each specific customer.
The CAS resides in a Server located near the Digital Headend and it also interfaces with the SMS (Subscriber Management System) and the Billing System.
An example of a single-channel ATSC transmitter system (capable of transmitting 1 to 6 TV programs) is shown in this block diagram:
The key system components are the Digital Headend for generating and processing the digital signal, the TV transmitter (which usually includes a modulator) and transmitting antenna subsystem.
In the (common) case where the program or programs to be transmitted originate from a TV studio located some distance away from the TV transmitter 9which is usually on a hill), it is necessary to install a microwave link (called an STL or Studio to Transmitter Link) for transporting digital signal to the transmitter.
Here is an example of the same system with an additional STL :