Verilink PRISM 3030 (34-00208.L) Product Manual - Manual (Page 97)

Ground Start Signalling (FXS) 87
The received signalling state causes the FXS application module to ground the tip
toward the CPE equipment. The CPE equipment removes the ring ground within
210 milliseconds. Within 1 millisecond after removing the ring ground, the CPE
equipment provides loop closure on the 2 -wire loop. The FXS application module
transmits both A and B signalling bits equal to 1 and enables the audio path.
Loop status of the CPE equipment is then transmitted toward the network
equipment by the FXS application module using the A signalling bit (0 equals loop
open and 1 equals loop closed). Dial pulses are transmitted transparently from the
CPE to the network equipment in this manner.
Call
Terminated
by CPE
The CPE opens tip to ring termination which causes the FXS application module
to transmit signalling bit A equal 0 and signalling bit B equal 1 towards the
network equipment. After a time-out period, the network equipment determines
that the CPE has disconnected. The network equipment then responds and the FXS
receives an A bit equal 1 and ignores the B bit. This causes the FXS application
module to open the tip, which is the idle state.
Ground Start
Incoming Call (from
network to CPE) In an idle state, the FXS application module sees the following.
✦ From the network, the received A bit equal to a 1 and the B bit ignored
✦ The tip is open toward the CPE
✦ No ring conductor ground from the CPE
✦ No loop termination from the CPE.
Upon incoming seizure from the network, the FXS application module receives an
A bit equal to 0. The FXS application module grounds the tip conductor towards
the CPE. The reception of a B bit equal to 0 causes the FXS application module to
send ring voltage to the CPE. When the CPE terminates the loop, the FXS
transmits both A and B signalling bits equal to 1 toward the network, terminates
ringing, and enables the audio path.
Ground Start Call
Termination
(CPE end)
The CPE removes loop termination which causes the FXS application module to
transmit the A signalling bit equal to a 0 and the B signalling bit equal to a 1. The
network equipment returns an A signalling bit equal to 1. When the FXS receives
the A signalling bit equal 1, it opens the tip conductor toward the CPE.
Ground Start
Call Termination
(by the network)
With both the CPE and the network in conversation mode and off hook, the FXS
application module is providing
−
48 VDC on ring and ground on tip toward the
CPE. The CPE is providing a loop closure toward the FXS application module.
The FXS application module is transmitting A and B bits equal to 1 toward the
network. The FXS application module is receiving A bits equal to 0 and B bits
equal to 1 from the network.
When the network disconnects, the FXS application module receives an A bit
equal to 1 (B is ignored) from the network. The FXS application module then