Specifications

Configuration Tasks

Cisco IOS Release 12.0(3)T

— E&M Immediate Start

In the Immediate Start protocol, the originating side does not wait for a wink before sending

addressing information. After receiving addressing digits, the terminating side then goes

off-hook for the duration of the call. The originating endpoint maintains off-hook for the

duration of the call.

• Ground Start / FXS—Ground Start signalling was developed to aid in resolving glare when two

sides of a connection tried to go off-hook at the same time. Two sides of the connection

simultaneously going off-hook creates a problem with loop start signalling because the only way

an incoming call from the network was recognized by the customer premise equipment (CPE)

using loop start was to ring the phone. The 6-second ring cycle left a substantial amount of time

for glare to occur. Ground Start signalling eliminates this problem by providing an immediate

seizure indication from the network to the CPE. This indication tells the CPE that a particular

channel has an incoming call on it. Ground Start is different than E&M in that the A and B bits

do not track each other (that is, A is not necessarily equal to B). When the CO delivers a call, it

“seizes” a channel (goes off-hook) by setting the A bit to 0. The CO equipment also simulates

ringing by toggling the B bit. The terminating equipment goes off-hook when it is ready to

answer the call. Digits are usually not delivered for incoming calls.

Channelized T1 Robbed-Bit Features

Internet service providers can provide switched 56-kbps access to their customers using the

Cisco AS5300. The subset of T1 CAS (robbed bit) supported features are as follows:

Supervisory: Line Side

• fxs-loop-start

• fxs-ground-start

• sas-loop-start

• sas-ground-start

• Modiﬁed R1

Supervisory: Trunk Side

• e&m-fgb

• e&m-fgd

• e&m-immediate-start

Informational: Line Side

• DTMF

Informational: Trunk Side

• DTMF

• MF