Verilink PRISM 3030 (34-00208.L) Product Manual Instrukcja Użytkownika Pobierz pdf (Strona 96)

86 APPENDIX B: FXS VOICE APPLICATION MODULE

Loop Start

Signalling (FXS)

Idle The application module has ground applied to the tip conductor and has −48 VDC

applied to the ring conductor towards the 2-wire loop. The 2-wire loop is open

(no DC path between the tip and ring conductors). The transmit A bit is set to 0

and the B bit is set to 1. The receive A bit (from the FXO application module) is

set to 0 and the B bit is set to 1.

Ringing During ringing, the office end (FXO) changes the state of the B bit from a 1 to a 0

and holds the A bit to a 0. The FXS application module detects the change in state

of the B bit and reacts by applying the ring generator to the 2-wire loop.

The ringing cadence (typically two seconds on and four seconds off) is provided

from the office end and is controlled by the 0 or 1 state of the B bit. The phone

rings until the call is abandoned by the calling party (FXO end) or the called party

goes off-hook.

Off-Hook/

Ring Trip

During ringing, the FXS application module is looking for an off-hook (loop

closure) condition. When the FXS detects the off-hook, the FXS application

module sets the A bit from a 0 to a 1. The B bit remains set at 1.

FXO Answer

Supervision

The change in the state of the receive A bit status from a 0 to a 1 causes the FXO

to place a loop closure on the 2-wire path toward the CO switch. This loop closure

trips the CO ringing and cuts through the voice path. The call is now complete.

Call

Request

The user goes off-hook at the FXS end. The FXS unit detects the off-hook and

signals the office end by changing the state of the A bit from a 0 to a 1. The B bit

remains set at 1. The FXO application module responds by placing a loop closure

on the 2-wire towards the CO switch. The CO switch responds by returning dial

tone to the FXS end. The user detects a dial tone and dials out using either dial

pulse or DTMF. The dial pulse toggles the state of the A bit at a rate of 10 pulses

per second (60 percent make and 40 percent break).

Ground Start

Signalling (FXS)

Idle The FXS application module has the tip conductor open and −48 VDC applied to

the ring conductor toward the 2-wire loop. The 2-wire loop is open (no DC path

between the tip and ring conductors). The transmit A bit is set to 0 and the

transmit B bit is set to 1. The receive A bit equals 1 and the receive B bit is

ignored.

Outgoing Call

(toward T1

Carrier)

The ring conductor is grounded by the CPE equipment on the 2-wire loop. This

causes the FXS application module to transmit both A and B signalling bits equal

to a 0. The network equipment responds and the FXS application module receives

a signalling bit equal to 0 and a B signalling bit equal to 1.

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