Cisco Voice T1, E1, IsDN Configuration and Troubleshooting

Cisco Voice T1, E1, ISDN Configuration And Troubleshooting

Types of Signalling

1) Ground start signalling:

2) Supervisory signalling:

off hook--connection between ring and tip wires-closed circuit

on hook--open circuit

Ringing

3) Information signalling:

Dial tone , Busy, ringback, congestion, Re-order, receiver off hook

4) Address signalling:

DTMF, Pluse

General Information

Tip ---->positive side of connection

Ring---->negative side of connection

Normally telephone is open circuit

Loop start signalling--->when phone lifted, the phone connects two wires causing current to flow from

central office

Glare occures in Loop start--Glare ----->when u pick the phone to dial number and simultaneously an

incoming call comes and before it has the chance to ring.

Digital Trunks:

CAS--Common associated signalling --signalling information is transmitted using same bandwidth as

voice.

CAS is sometimes called robbed-bit signaling because user bandwidth is robbed by the network for

signaling.

CCS--Common channel signalling --a separate channel is allocated for signalling part

http://cucmandgwconf.blogspot.com/2014/01/cisco-voice-t1-e1-isdn-configuration.html

T1 & E1

T1: Uses TDM to transmit digital data over 24 voice channels using CAS. There is no need for signalling

channel since for CAS signalling is transferred with data channel itself.

CAS Provides receipt and capture of DNIS(dialed number identification service) and ANI(automatic

number identification)

The most common signalling used with T1 CAS is E&M signalling

E1: Uses TDM to transmit digital data over 30 voice channels using either CAS or CCS.

ISDN: Circuit switched telephone network system allowed to digital transmission of voice and data over

ordinary copper wires.

ISDN BRI :128 kb/s ;2 B channels; 1 D channel

T1 PRI :1.5Mbps; 23 B channels ; 1 D channel

PRI NFAS : Multiple ISDN PRI interfaces controlled by single D channel.

QSIG: Interopeartion of PBX from different vendors.

Three types of digital voice circuits are available

1)T1 uses TDM to transmit 24 voice channels using CAS

2)E1 uses to transmit 30 voice channles using either CAS or CCS

3)ISDN: A circuited swicthed telephone network using CCS

Ø BRI: 2 B (Bearer) channels and 1 D (Delta) channel

Ø T1 PRI: 23 B channels and 1 D channel

Ø E1 PRI: 30 B channels and 1 D channel

Channels are known as DS0 channels, The ds0-group command creates a logical voice port (a DS0 group)

from some or all of the DS0 channels

Two main types of CAS are

T1 CAS

E1 R2 Trunk

T1 CAS:

The type of signaling most commonly used with T1 CAS is E&M signaling

The main disadvantage of CAS signaling is its use of user bandwidth to perform these signaling functions.

The voice device running the T1 line uses the eighth bit on every sixth FRAME in each T1 channel (DS0)

for signalling.

There are 24 Frames in a T1 Extendede super Frame, the process of signalling occurs for every sixth

frame. 12 frames in super frame.

Each DSO = 8 bits

24 DS0 = 8*24 +1 bit =193 bits ( 1 bit added was for framing bit)

Digital T1 lines send 8000 of these 193-bit frames every second

8000*193 =1.5444Mbps

E1 R2

Ø A multiframe consists of 16 consecutive 256-bit frames.

Ø Each frame carries 32 time slots.

Ø The first time slot is used exclusively for frame synchronization.

Ø Time slots 2 to 16 and 18 to 32 carry the actual voice traffic, and time slot 17 is used for R2 signaling.

Ø 16 Frames == Multi frame in E1 R2

Ø 1st frame--- time slot 17 is to declare the Frame as multiframe.

Ø 2. Frame, Time slot 17: Signaling for time slots 2 and 18

Ø 3. Frame, Time slot 17: Signaling for time slots 3 and 19

Ø It goes on like tat

ISDN:

ISDN comprises digital telephony and data-transport services offered by regional telephonecarriers.

ISDN involves the digitization of the telephone network, which permits voice, data, text, graphics, music,

video, and other source material to be transmitted overexisting telephone wires.

In contrast to the CAS and R2 signaling, which provide only DNIS, ISDN offers additional supplementary

services such as Call Waiting and Do Not Disturb (DND).

ISDN applications include high-speed image applications (such as Group IV facsimile), additional

telephone lines in homes to serve the telecommuting industry, high-speed file transfer, and video

conferencing. Voice service is also an application for ISDN.

ISDN BRI: 2 bearer channel(64kbps) ( for voice traffic)+ 1 D channel (16kbps)(D channel for signalling)

ISDN PRI: 23 B + 1 D(64kbps) in north america and 30 B +1 D in rest of the world

T1 PRI: Use this interface to designate North American ISDN PRI with 23 B channels and one CCS channel

E1 PRI: Use this interface to designate European ISDN PRI with 30 B channels, one CCS channel, and one

framing channel.

ISDN-PRI Nonfacility Associated Signaling (NFAS): Multiple ISDN PRI interfaces controlled by single D

channel.

Benefits of ISDN:

ISDN has a built-in call control protocol known as ITU-T Q.931.

ISDN supports call waiting, call forwarding,speed dialing

T1 line encoding are B8ZS(binary 8-zero substitution), AMI and E1 line encoding are high-density bipolar

3(HDB3), AMI

CLOCKING:

free-running --not typical used(neither gets the clock nor it supplies)

line --service provider is giving the clock

internal ---u r providing the clock (in case u are connecting to pbx)

show network-clocks ----- command in order to verify the clocking configuration

Single voice port receiving internal clocking.

Line receives the clock from the PSTN

Configuration :

Router2(config)#controller T1 1/0

Router2(config-controller)#framing esf

Router2(config-controller)#linecoding ami

Router2(config-controller)#clock source line

Router2(config-controller)#ds0-group timeslots 1-12 type e&m-wink-start

Internal clocking:

Internal clock supplies the clock to the PBX

Router1(config)#controller T1 1/0

Router1(config-controller)#framing crc4

Router1(config-controller)#linecoding hdb3

Router1(config-controller)#clock source internal

Router1(config-controller)#ds0-group timeslots 1-15 type e&m-wink-start

Clock Prioritize when When two PSTN Lines are connected

network-clock-select 1 e1 0/0

network-clock-select 2 e1 0/1

By default WIC cards are disabled for receving the clock--so you have to configure which wic card will

receive the clocking from PSTN. Go to the global configuration mode and type the command as below

network-clock-participate wic 1 (receving clock)

Note: When two or more controllers are configured for line, one should be designated as the primary

clock source; it drives the other controllers.

Router(config-controlle)#clock source line primary

Router(config-controlle)#clock source line secondary 1

Configuration of T1:

DSO groups:

Dso groups can be deactivated only when the voice port is deactivated.

1) Defines the T1/E1 channels for compressed voice calls

2) Automatically creates a logical voice port

3) Defines the emulated analog signaling method the router uses to connect to the PBX or PSTN

T1 CAS Controller Configuration Example

Enter controller configuration mode.

Router(config)#controller {t1 | e1} slot/port

Select frame type for T1 or E1 line.

Note: The service provider determines the framing type that is required for your T1/E1 circuit

T1 Lines:

Router(config-controller)#framing {sf | esf}

E1 Lines:

Router(config-controller)#framing {crc4 | no-crc4} [Australia]

Router(config-controller)#clock source {line [primary | bits] |internal | free-running}

Define the T1 channels for use by compressed voice calls and the signalling method the router uses to

connect to the PBX or CO.

Router(config-controller)#ds0-group ds0-group-number timeslots

timeslot-list [service service-type] type {e&m-fgb | e&m-fgd | e&mimmediate-

start | fgd-eana | fgd-os | fxs-ground-start | fxs-loop-start

| none | r1-itu | r1-modified | r1-turkey}

The ds0-group command automatically creates a logical voice port. The resulting logical voice port will

be 1/0:1, where 1/0 is the module and slot

number and :1 is the ds0-group-number argument you assign in this step.

5)Activate the controller.

Router(config-controller)#no shutdown

Digital Voice Port Parameters

After setting up the controller, you can configure voice port parameters for that digital

voice port. When you specified a ds0-group, the system automatically created a logical

voice port

Enter voice-port configuration mode.

Router(config)#voice-port slot/port:ds0-group-number

Router(config-voiceport)#cptone locale

Activate the voice port.

Router(config-voiceport)#no shutdow

Configuring T1 CAS Trunks: Inbound E&M FGD and Outbound FGD EANA

Follow this procedure to configure a T1 CAS digital voice port with inbound and outbound

ANI:

Step 1. Enter controller configuration mode.

Router(config)#controller T1 0/0/0

Step 2. Specify the framing format.

Router(config-controller)#framing esf

Step 3. Specify line coding.

Router(config-controller)#linecode b8zs

Step 4. Configure one DS0 group to use time slots 1 to 12 and E&M feature group-D.

Router(config-controller)#ds0-group 0 timeslots 1-12 type e&m-fgd

Step 5. Configure another DS0 group to use time slots 13 through 24 and E&M feature group-D EANA.

Router(config-controller)#ds0-group 1 timeslots 13-24 type fgd-eana

Chapter 4: Performing Call Signaling over Digital Voice Ports 217

Note This creates two voice ports, 0/0/0:0 and 0/0/0:1.

Step 6. An inbound dial peer is configured using the 0/0/0:0 trunk, which supports inbound ANI:

Router(config)#dial-peer voice 1 pots

Router(config-dialpeer)#incoming called-number .

Router(config-dialpeer)#port 0/0/0:0

An outbound dial peer is configured using the 0/0/0:1 trunk, which supports

outbound ANI:

Router(config)#dial-peer voice 90 pots

Router(config-dialpeer)#destination-pattern 9T

Router(config-dialpeer)#port 0/0/0:1

Example T1 CAS Trunk Configuration Example

Router4(config)#controller T1 0/0/0

Router4(config-controller)#framing esf

Router4(config-controller)#linecode b8zs

Router4(config-controller)#ds0-group 0 timeslots 1-12 type e&m-fgd

Router4(config-controller)#ds0-group 1 timeslots 13-24 type fgd-eana

Router4(config)#dial-peer voice 1 pots

Router4(config-dialpeer)#incoming called-number .

Router4(config-dialpeer)#direct-inward-dial


Router4(config-dialpeer)#destination-pattern 9T

Router4(config-dialpeer)#port 0/0/0:1

Example E1 R2 Trunk Configuration

Router5(config)#controller E1 0/0/0

Router5(config-controller)#ds0-group 0 timeslots 1-31 type r2-digital r2-compelled ani

Router5(config-controller)#cas-custom 0

Router5(config-ctrl-cas)#country china use-defaults


Router5(config-dialpeer)#destination-pattern 9T

Router5(config-dialpeer)#direct-inward-dial

Router5(config-dialpeer)#port 0/0/0:0

Configuration of ISDN:

isdn incoming-voice: Configures the interface to send all incoming calls to the DSP card for processing

interface serial ---Enter voice port configuration mode for the D channel

Router(config)#isdn switch-type primary-qsig

Router(config)#controller t1 0/0

Router(config-controller)#pri-group timeslots 1-24

Router(config-controller)#interface serial 0/0:23

Router(config-if)#isdn incoming-voice voice

Configuring a PRI Trunk Example

network-clock-participate wic 0 ----The DSP clocking will be synchronized with the WIC in slot 0.

The line coding for the E1 controller will be linecoding ami-- default

Router2(config)#interface Serial0/0/0:15---16 line will be the signalling channel

Performing Call Signaling over Digital Voice Ports 225

Router2(config)#network-clock-participate wic 0

Router2(config)#isdn switch-type primary-net5

Router2(config)#controller e1 0/0/0

Router2(config-controller)#pri-group timeslots 1-31

Router2(config)#interface Serial0/0/0:15

Router2(config-if)#isdn switch-type primary-net5 Router(config-if)# isdn overlapreceiving

Router2(config-if)#isdn incoming-voice voice

Summary of voice ports:

Router#show controller T1 1/0/0

Router#show voice dsp

Router#show voice call summary

show voice port summary -----command to identify the port numbers of voice interfaces installed in

your router.

show call active voice ---- command to display the contents of the active call table, which shows all the

calls currently connected through the router or concentrator.

show call history voice ------command to display the contents of the call history table.

QSIG:

Example Global QSIG Support Configuration for BRI

Router(config)#isdn switch-type basic-qsig

Example Global QSIG Support Configuration for PRI

Router(config)#isdn switch-type primary-qsig

Specify the card type (T1 or E1) at the specified slot so the router provides sufficient DSP resources.

Router(config)#card type t1

Example QSIG over PRI Interface Configuration

Router(config)#controller t1 0/1

Router(config-controller)#pri-group timeslots 1-24

Router(config)#interface serial 0/1:23

Router(config-if)#isdn switch-type primary-qsig

Router(config-if)#isdn protocol-emulate user

Example QSIG over BRI Configuration

Router(config)#interface bri 1/1

Router(config-if)#isdn layer1-emulate user


Router(config-if)#isdn layer1-emulate network

Router(config-if)#isdn incoming-voice voice

Router(config-if)#isdn protocol-emulate user


Router(config-if)#isdn protocol-emulate network

Example show isdn status Command

Router#show isdn status

The show isdn status command shows tat Layer 1 =active and layer

2="MULTIPLE_FRAME_ESTABLISHED" indicates that there is no

problem with layer 1 and 2

If a TEI_UNASSIGNED or AWAITING_ESTABLISHMENT state is reported, verify the configuration

Global ISDN Switchtype = primary-qsig

ISDN Serial0/1/1:23 interface

dsl 0, interface ISDN Switchtype = primary-qsig

**** Slave side configuration ****

Layer 1 Status:

ACTIVE

Layer 2 Status:

TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED

Layer 3 Status:

0 Active Layer 3 Call(s)

Active dsl 0 CCBs = 0

The Free Channel Mask: 0x00000000

Number of L2 Discards = 0, L2 Session ID = 0

Total Allocated ISDN CCBs = 0

CONFIGURATION OF T1

You should get the following details from the service provider

1) Framing

2) Line coding

3) Clock source

Check using below commands

show controller t1 --->only shows the E1 or T1 and also the port/slot connected.

show voice port summary

show ip int brief

T1 configuration:

conf t

controller t1 0/1/0 (slot/sub-unit/port)

framing esf

linecode b8zs

clock source line

no shutdown

CAS Digital Connections:

T1 ==24DS0 (Digital service level)

1 DSO =64Kbps

dso-group number is between 0 to 23 for T1 and 0 to 30 for E1.

controller t1 0/1/0

ds0-group 0 timeslots 1-2 type e&m-immediate-start

ds0-group 10 timeslots 1-4 type fxo-loop-start (fxo-loop start is mostly used in PSTN connection )

Note for troubleshooting:

Not enough DSP resources when getting configurating the t1-->limit the number of slots and try or

else add dsp

CCS ISDN Configuration:

After creating prigroup u will get the serial interfaces serial0/1/0:0 and will get voice port: voice-card

0/1/0:D port.

conf t

isdn swith-type primary-qsig

controller t1 0/1/0

pri-group timeslots 1-4

When u configure then it u will be getting four serial ports

serial0/1/0:0 serial0/1/0:1 serial 0/1/0:2 serial 0/1/0:3

There is additional port created for signalling and it is serial0/1/0:23

Configure the Interface(serial ports)

interface serial0/1/0:0

The following example for channelized T1 configures the D channel (hence, all B channels) to answer all

incoming voice calls at 56 kbps:

interface serial 0:23

isdn incoming-voice data 56

NOTE:

for full time slot assignment: pri-group timeslots 1-24 (T1) pri-group timeslots 1-31 (E1) another e.g

pri-group timeslots 1-10,23

If the controller is of type T1, then the 24th timeslot is for the control information. ie., Serial x:23

functions as the D-channel.

If the controller is of type E1, then the 16th timeslot is for the control information. ie., Serial x:15

functions as the D-channel.

Incoming call:

isdn incoming-voice voice -------->Configures incoming voice calls bypass the modems and be handled as

a voice call.

isdn incoming-voice modem-->Incoming voice calls are passed over to the digital modems, where they

negotiate the appropriate modem connection with the far-end modem.

The incoming-voice modem command will allow the router (Gateway Example:AS5400) to process

inbound calls (tones) for both voice and data. In other words, fax and modem tones as well as voice will

be handled accordingly

ISDN-QSIG:

isdn switch-type primary-qsig -----> PRI

isdn switch-type basic-qsig ----> BRI

ISDN Status:

show isdn active----->Shows ISDN calls in progress

show isdn history------>Shows ISDN call history

show isdn status------->Shows ISDN line status

show isdn timers-------->Shows ISDN timer values

debug isdn events------->Displays ISDN events in real time

debug isdn q921--------->Displays ISDN Q.921 packets in real time

debug isdn q931 -------->Displays ISDN Q.931 packets in real time

Transparent CCS configuration:

This is for Different signalling protocols(for e.g Nortel to communicate with nortel PBX over the WAN)

For T1 its the 24 time slot used for signalling and E1 16 time slot

conf t

controller t1 0/1/0

ds0-group 23 timeslot 24 type ext-sig

T1 & E1

T1: Uses TDM to transmit digital data over 24 voice channels using CAS. There is no need for signalling

channel since for CAS signalling is transferred with data channel itself.

CAS Provides receipt and capture of DNIS(dialed number identification service) and ANI(automatic

number identification)

The most common signalling used with T1 CAS is E&M signalling

E1: Uses TDM to transmit digital data over 30 voice channels using either CAS or CCS.

ISDN: Circuit switched telephone network system allowed to digital transmission of voice and data over

ordinary copper wires.

ISDN BRI :128 kb/s ;2 B channels; 1 D channel

T1 PRI :1.5Mbps; 23 B channels ; 1 D channel

PRI NFAS : Multiple ISDN PRI interfaces controlled by single D channel.

QSIG: Interopeartion of PBX from different vendors.

Configuration Examples:

The following example shows how to configure a basic channelized E1 PRI ISDN port adapter. In this

example, the controller is enabled, timeslots are assigned to the PRI group, and the ISDN switch type

used on all ISDN interfaces on the router is a switch for the European community (primary-net5). The

PRI group timeslots of 1, 3, 4, 5, and 7 (the B channels) are selected to map to timeslot 16 (the D

channel), which is recognized by the system as timeslot 15.

Router# configure terminal

Router (config)# isdn switch-type primary-net5

Router (config)# controller e1 3/1/1

Router (config-controller)# framing crc4

Router (config-controller)# linecode hdb3

Router (config-controller)# pri-group timeslots 1,3-5,7

Router (config-controller)# exit

Router (config)# interface serial 3/1/1:30

Router (config-if)# ip address 1.1.15.1 255.255.255.0

Router (config-if)# end

The following example shows how to configure a basic channelized T1 PRI ISDN port adapter. In this

example, the controller is enabled, timeslots are assigned to the PRI group, and the ISDN switch type

used on all ISDN interfaces on the router is for the United States switch (primary-5ess). The PRI group

timeslots of 1, 3, 4, 5, and 7 (the B channels) are selected to map to timeslot 24 (the D channel), which is

recognized by the system as timeslot 23.


Router (config)# isdn switch-type- primary-5ess

Router (config)# controller t1 3/1/1

Router (config-controller)# framing esf

Router (config-controller)# linecode b8zs

Router (config-controller)# pri-group timeslots 1,3-5,7

Router (config-controller)# exit

Router (config)# interface serial 3/1/1:23



Router#

The following example shows channel group 0 and timeslots 1, 3 through 5, and 7 selected for mapping.

The example shows how to configure a basic channelized E1 port adapter on a Cisco 7200 series router:


Router (config)# controller e1 1/1

Router (config-controller)# clock source line

Router (config-controller)# framing crc4

Router (config-controller)# linecode hdb3

Router (config-controller)# channel-group 0 timeslots 1,3-5,7 ( channel group groups the time slot and

convert to single channel)

Router (config)# interface serial 1/1:0



Router#

T1 or E1 Interface Troubleshooting

To troubleshoot the T1 or E1 interface, perform the following steps:

SUMMARY STEPS

· show controller {t1 | e1}

· Check if the line is down.

· Check for reported alarms.

· Check for error events.

· Check if the interface is T1 or E1 CAS, E1 R2, or PRI.

Controller Has Loss of Frame:

Put command show controller {t1 | e1}. If there is any loss of frame try changing the frame type. If the

first framing format does not work, try the other framing format to see if the alarm clears.


Enter configuration commands, one per line. End with CNTL/Z.

Router(config)# controller t1 0

Router(config-controlle)# framing esf

For T1 lines, change the line build-out using the cablelength long or cablelength short command.

Contact your service provider for framing and line coding settings. Common settings are as follows:

For T1 lines, it is common to use binary 8-zero substitution (B8ZS) line coding with extended superframe

(ESF), and alternate mark inversion (AMI) line coding with superframe (SF).

For E1 lines, both HDB3 and AMI line coding are available, but CRC4 framing is most widely used.

E.G OF SHOW CONTROLLER COMMAND:

show controllers t1 0

T1 0 is up.

Applique type is Channelized T1

Cablelength is long gain36 0db

No alarms detected.

Version info of slot 0: HW: 4, Firmware: 16, PLD Rev: 0

Manufacture Cookie Info:

EEPROM Type 0x0001, EEPROM Version 0x01, Board ID 0x42,

Board Hardware Version 1.32, Item Number 73-2217-5,

Board Revision B16, Serial Number 09356930,

PLD/ISP Version 0.0, Manufacture Date 18-Jun-1998.

Framing is ESF, Line Code is B8ZS, Clock Source is Line Primary.

Data in current interval (8 seconds elapsed):

0 Line Code Violations, 0 Path Code Violations

0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins

0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

The main items to look at in the above output is

1)The status of the line

2)Alarms

Linecode and Pathcode violations

3) Slip Secs: If timing differs then voice quality,noice problems in the call arises

In most cases, you can check for clock slips on the E1 or T1 interface in order to confirm the problem.

Issue the show controller {e1 | t1} command for confirmation:

Router# show controller e1 0/0

E1 0/0 is up.

Applique type is Channelized E1 - balanced

No alarms detected.

alarm-trigger is not set

Version info Firmware: 20020812, FPGA: 11

Framing is CRC4, Line Code is HDB3, Clock Source is Line.

Data in current interval (97 seconds elapsed):

0 Line Code Violations, 0 Path Code Violations

4 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins

4 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

A common message you will see in the alarm field is "receiver has loss of frame." ---->check framing is

correct

Another message you might receive is "receiver is getting AIS." ----->This means the receiver is getting an

alarm indication signal (blue alarm)

This is typically seen when the far-end CSU has lost its terminal side equipment. The "receiver has

remote alarm" indicates the presence of a yellow alarm. This means the downstream CSU is in a loss-of-

frame or loss-of-signal state. Therefore, the remote CSU has a red alarm.

The "transmitter is sending remote alarm" indicates that the local CSU has detected either a loss-of-

frame or loss-of-signal condition

Always verify framing and T1 signal when troubleshooting this problem.

Whenever you are troubleshooting a T1, always verify that both-sides of the circuit are running clean. It

is possible that only one side of the T1 is seeing errors. Remember, that the T1 is going only between

you and the provider. Always contact the provider to make sure they aren't seeing errors on their side of

the circuit.

Troubleshooting the ISDN connection:

show isdn status

E.g output of the command:

ISDN BRI3/0 interface

dsl 16, interface ISDN Switchtype = basic-ni

Layer 1 Status:

ACTIVE

Layer 2 Status:



TEI 64, ces = 1, state = 5(init)

spid1 configured, spid1 sent, spid1 valid

Endpoint ID Info: epsf = 0, usid = 0, tid = 1

TEI 73, ces = 2, state = 5(init)

spid2 configured, spid2 sent, spid2 valid

Endpoint ID Info: epsf = 0, usid = 1, tid = 1

Layer 3 Status:

0 Active Layer 3 Call(s)

Active dsl 16 CCBs = 0

The Free Channel Mask: 0x80000003

Total Allocated ISDN CCBs = 0

To determine whether everything is copacetic, you should look for three main things in this output:

Layer 1 Status should say Active.

Layer 2 Status should say MULTIPLE_FRAME_ESTABLISHED.

Under Layer 2, spid1 and spid2 should both say configured and valid.

If Layer 1 is down

Calling the carrier and opening a ticket for a Layer1 Down status, let's keep investigating. On the

interface, try using the clear isdn interface bri0/0 command and the no shutdown command.

REFERENCE WEBPAGES:

http://ccie-security.blogspot.com/2008/10/t1-wierdness.html

http://docwiki.cisco.com/wiki/Cisco_IOS_Voice_Troubleshooting_and_Monitoring_--

_T1_or_E1_Interface_Troubleshooting#Troubleshooting_T1_and_E1_Layer_1_Problems

Documents

Cisco Voice T1, E1, IsDN Configuration and Troubleshooting