Eicon Networks ISDN NT1 Especificaciones descargar pdf (Pagina 19)

The analogue signal originating in the microphone of the telephone handset is sampled

and transformed into a stream of bits (64 000 of them every second) that is placed on the

B channel.

Similarly, the incoming bit stream from the B channel is converted back into an analogue

signal and sent to the ear-piece of the handset.

A B channel is full duplex, which means that it can carry data in both directions at once.

The ability to make voice calls from one ISDN telephone to another over a digital B

channel is indeed useful, however, the majority of telephones currently installed worldwide

are analogue devices which are not connected to an ISDN.

Fortunately, you can make calls between the two networks. For this to work successfully,

there has to be a conversion between the bit stream in the B channel and the analogue

signal required by the PSTN.

CODECs are located at the boundaries of the digital and analogue networks.

Fortunately, you can make calls between the two networks. For this to work

The CODECs inside the network and the telephone must use the same rules when

formatting the bit stream that represents the users' voices. Provided both devices doing

the same processing, then the information can be converted by applying the same rules in

reverse.

Given the presence of the CODEC in the network, and adherence to the correct protocols,

any device that can be used on the PSTN, such as a modem or a fax machine, can also

pass calls into the ISDN.

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Eicon Networks ISDN NT1 Especificaciones Pagina 19