Dialogic 6.2 Manuale Utente

Loop Start Signaling

November 2009

302

Brooktrout modules support two types of loop start signaling:

„

FXO Loop Start

„

FXS Loop Start

When operating in FXO mode, the module assumes the far end of the 

connection is an FXS termination. When operating in FXS mode, the 

module assumes the far end is an FXO termination.

FXS Loop Start is the protocol used for Brooktrout's analog modules. 

The sequence of events and timings is the same for both analog or 

digital line interfaces.

The timing diagrams in this section show the Receive and Transmit 

Signaling Bits in reference to the digital signaling mode. The analog 

signals are a direct mapping of the signaling bits.

In the FXS diagrams, the electric signals sent by the station are 

represented in bit A: loop current presence (off-hook) is represented 

by setting bit A high (one); absence (on-hook) by bit A low (zero). Bit 

B does not change. The signals received by the station, ring signal 

and loop current feed (battery), are represented using both A and B 

bits: loop current feed is represented by setting bit A low (zero); 

absence by bit A high (one). Presence of ring signal is represented by 

setting bit B low (zero); absence by bit B high (one).

The FXO diagrams are the mirror-image of the FXS diagrams. The 

signals sent by the module (FXO) toward the network (FXS) are the 

same that the station (FXS) received from the network (FXO) on the 

FXS diagrams.