Integrated Reception Systems (IRS)
Posted on 30th April at 10:12 AM
About Intergrated Reception Systems (IRS)
An Integrated Reception System (IRS) is in effect a MATV system that has been extended to carry satellite signals as well as analogue and DTT signals. It provides a greater choice for users but has a higher initial cost than a MATV system.
Satellites provide a greater capacity for signals. To avoid problems that would arise if the whole range of satellite signals were carried on a single cable, a quarter of the signals are carried on each of four parallel trunk cables. Terrestrial signals are carried on a fifth trunk. This type of system, commonly known as a “five-wire system”, is therefore quite complex.
Connecting to an IRS
In a typical IRS system, residents can connect their TV set or digital receiver to the socket outlet in their home, in the same way as with a MATV system, but they can also connect a satellite receiver. The receiver sends commands to a “multi-switch”, which connects it to the most appropriate of the four trunk cables, to deliver the desired signal. The terrestrial signals on the fifth wire are always sent to all users. Satellite signals use different frequencies from terrestrial signals, so it is possible to combine the two signals onto the single wire to the user without interference.
In smaller systems, only a single multi-switch is required, and it is usually located at roof level, close to the aerials feeding it. Larger systems can have single or multiple multi-switches, typically with 12 outputs each. Multiple multi-switches are connected to a common “backbone” of “trunk cables” that, in a tower block for example, may run through a central riser or be fixed to the outside of the building. Cost savings can be made by locating the multi-switches on each floor of the building, minimising the amount of cable required.
This process delivers satellite signals to receivers exactly as if they were connected directly to their own satellite dishes, so the user needs no special equipment. However, with only a single cable from the multi-switch to the outlet in each household, only one satellite receiver can be connected at any one time, otherwise a conflict between the commands sent by two different receivers would arise. Therefore the use of a personal video recorder (such as Sky+), designed to allow one programme to be watched while recording another, or use of two satellite-viewing TV sets in a household will require two separate feeds. Installing two separate feeds to each household, each feed occupying its own output on the multi-switch with a separate cable, can increase system costs, but it is becoming standard practice and the preferred option for residents.
Other Language Satellite Services
When there are many residents whose first language is not English, it is quite common to have additional dishes pointing at different satellites. For each additional satellite, a further four wires must be added to the system, and the number of connections to the multi-switch increased correspondingly. Nine-wire systems are quite commonly found, and even some 13-wire systems exist.
Other Services
When upgrading MATV systems to IRS, distribution cabling must be replaced. Both MATV and IRS systems can be enhanced to carry a range of other services, such as video from security cameras and door entry systems, and online services such as email, internet access and connection to e-government services. Pilot projects involving data services have been carried out by Glasgow Housing Association and in the London Borough of Newham.
Webfeed
