RAB-P 601 is a system to satisfy the ISDN Basic Access connection requirements even in areas not yet covered by the new technology.

The product will in fact relay one or two ISDN basic accesses to a remote exchange using the data channels of the HF transmission network, with the 2B1Q line code as defined by the ETSI telecommunications standards. Connection is performed by a pair of RAB-P systems:

	one system, connected directly to the ISDN exchange originating the BRA (Basic Rate Access) connection;
	the second system installed in the remote exchange to which the subscriber is connected.

The first converts the signal of the basic access into signals that are compatible with the 64 Kb/s High Frequency channels carrying the information. The second system performs the inverse operation, i.e. it converts the signals coming from the HF channels into signals that are compliant with the ISDN basic access standard, with line code 2B1Q.

With RAB-P, the connection between ISDN exchange and subscribers is completely transparent as the exchange sees the NT (Network Terminator) unit at the subscriber site as though it were connected to it directly. The same transparency is guaranteed in the opposite direction (Subscriber-Exchange).

Synchronization of the timing between the local system and the remote one is assured through connection to a 2 Mb/s PCM stream, HDB3. The sync signals are extracted from these streams without any alteration of their contents.

The RAB-P 601 system, on account of its dimensions and shape, can be installed directly on a HF concentrator and is ideal for use in situations where the ISDN Basic Access activation requests are limited to a few units or where the service activation times have to be particularly fast.