Signaling protocols

In addition to the voice signals that are sent to and from the caller, other signaling information is also sent to and from the switch, to enable such functions as:

A variety of signaling protocols provide some or all of these functions. Functions that are supported by T1 protocols are listed in Table 1, and functions that are supported by E1 protocols are listed in Table 2. Before deciding on or configuring a specific protocol, you must ensure that your central office switch, PSTN, PABX, or channel bank can also support the required functions. More information about the protocols is given in the Blueworx Voice Response for AIX: General Information and Planning information.

Table 1. Functions provided by T1 protocols.

For each T1 protocol, this table shows if it is a trunk-side or a line-side protocol, whether or not PSTN, PABX, and channel bank connectivity are supported, and also whether or not answer detection, call transfer, far-end disconnect, ANI, and DID or DNIS are supported.

Protocol

Type 9

Connectivity

Function

 

PSTN

PABX

Channel bank

Answer detection

Call transfer

Far-end disconnect

ANI

DID or DNIS

E&M1

Trunk

Yes

Yes

Yes2

Yes

No3

Yes

Yes

Yes

FXS Loop Start 1

Line

Yes

Yes

Yes2

No

Yes

No4

No5

No 5

SAS Loop Start

Line

Yes

Yes

Yes

No

Yes

No4

No5

No 5

FXS Ground Start 1

Line

Yes

Yes

Yes 2

No

Yes

Yes

No 5

No 5

ISDN (5ESS 5E9)

Trunk

Yes

No

Yes6

Yes

No

Yes

Yes

Yes

ISDN (5ESS 5E12)

Trunk

Yes

No

Yes6

Yes

No

Yes

Yes

Yes

ISDN (T1 National 2)

Trunk

Yes

No

Yes6

Yes

No

Yes

Yes

Yes

ISDN (DMS100 BCS34/36)

Trunk

Yes

No

Yes6

Yes

No

Yes

Yes

Yes

ISDN (TR41449/41459)

Trunk

No

Yes

Yes 6

Yes

No

Yes

Yes

Yes

ISDN NA008 (DMS National)7

Trunk

Yes

No

Yes6

Yes

No

Yes

Yes

Yes

ISDN IEC05 (DMS250)8

Trunk

Yes

No

Yes6

Yes

No

Yes

Yes

Yes

ISDN(INS Net Service 1500)

Trunk

No

Yes

Yes6

Yes

No

Yes

Yes

Yes

In the Type column, Trunk means “trunk-side protocol” and Line means “line-side protocol”

Note:
  1. For both 2-bit AB (SF) format and 4-bit ABCD (ESF) format, as defined in TIA/EIA 464-B.
  2. A channel bank for 4-bit (ESF) format CAS signaling must support extended superframe (ESF) line framing.
  3. Yes, if the switch offers a release link trunk.
  4. Yes, if a disconnect clear signal is provided.
  5. Some PABX and ACD systems send number identification by sending DTMF digits before or after the call is answered.
  6. A channel bank for ISDN must support extended superframe (ESF) line framing.
  7. Supports RLT call transfer and two B-channel transfer.
  8. Supported RLT call transfer.
Table 2. Functions provided by E1 protocols.

For each E1 protocol, this table shows if it is a trunk-side or a line-side protocol, whether or not PSTN, PABX, and channel bank connectivity are supported, and also whether or not answer detection, call transfer, far-end disconnect, ANI, and DID or DNIS are supported.

Protocol

Type12

Connectivity

Function

 

PSTN

PABX

Channel bank

Answer detection

Call transfer

Far-end disconnect

ANI

DID or DNIS

E&M1

Trunk

Yes

Yes

Yes

Yes

No2

Yes

Yes

Yes

FXS Loop Start

Line

Yes

Yes

Yes

No

Yes

No3

No4

No4

EL7/CAS

Line

No

Yes5

No

Yes

Yes

Yes

No6

No6

Italy

Trunk

Yes

No

No

Yes

No

Yes

No

Yes

R27

Trunk

Yes

Yes

Yes

Yes

No

Yes

Yes

Yes

R2MFC8, 9

Trunk

Yes

No

No

Yes

No

Yes

Yes

Yes

RE

Line

No

No

Yes

No

Yes

No

No

No

SL10

Line

Yes

No

No

Yes

No

Yes

No

No

TS00311

Trunk

Yes

Yes

Yes

Yes

No

Yes

Yes

Yes

UK Callstream

Trunk

Yes

No

No

Yes

No12

Yes

No

No

UK Exchange

Trunk

Yes

No

No

Yes

No

Yes

No

No

UK Tie/DDI

Trunk

Yes

No

No13

Yes

No12

Yes

Yes

Yes

ISDN

Trunk

Yes

Yes

No

Yes

No

Yes

Yes

Yes

SS7 ISUP

Trunk

Yes

No

No

Yes

No

Yes

Yes

Yes

In the Type column, Trunk means “trunk-side protocol” and Line means “line-side protocol”

Note:
  1. For connection to Siemens Hicom 300 switch.
  2. Yes, if the switch offers a release link trunk or an ACL exchange data link is available.
  3. Yes, if a disconnect clear signal is provided.
  4. Some PABX and ACD systems send number identification by sending DTMF digits before or after the call is answered.
  5. Unique protocol for Ericsson MD110.
  6. Yes, if a VMS exchange data link is available on the MD110.
  7. R2 digital line signaling as specified by ITU-T Q.421.
  8. Korean only
  9. R2MFC uses R2 for line signaling
  10. Subscriber Loop, used in France.
  11. Multifrequency compelled (MFC) is not supported.
  12. Yes, to support ”inverted“ E&M.
  13. “Mid-call diversion” is supported.

Two classes of signaling protocol exist: channel associated signaling (CAS) and common channel signaling (CCS). In addition, an exchange data link (EDL) can be used with a CAS protocol to provide additional signaling functions.

Channel associated signaling

When channel associated signaling protocols, such as E&M wink start, or FXS loop start, carry the signaling information for a particular channel, they carry the information on either of the following:

This signaling information enables call control (call setup and clearing), but other functions, such as far-end hang up detection, are not necessarily provided by all channel associated signaling protocols.

Exchange data link

If your CAS protocol does not provide all the signaling functions that you need, you might be able to use an exchange data link; that is, a link from the switch to the pSeries computer on which Blueworx Voice Response runs. This link can carry additional signaling information to enable:

Exchange data link signaling protocols, such as ACL, SMDI, SMSI, and VMS, are typically used with trunks that use a channel associated signaling protocol for call control.

Alternatively, you can use CallPath Server to send additional information to and from the switch, including called and calling number, message waiting indication (MWI), and far-end hangup detection. The CallPath_SigProc signaling process that is used to communicate with CallPath Server is registered as an exchange data link, and needs to be configured in a similar way.

Note: Some switches restrict use of CallPath to trunks that use line-side protocols instead of trunk-side protocols (as shown in Table 1 and Table 2). Ask your switch manufacturer to verify that CallPath is supported.

Common channel signaling

Common channel signaling protocols, such as Signaling System Number 7 (SS7) and Primary Rate Integrated Services Digital Network (ISDN), carry allthe signaling information for many voice channels over a single, dedicated signaling link. The common channel signaling link can provide:

The signaling link is usually one 64 Kbps channel on a T1 or E1 trunk. Most common channel signaling protocols are based on the OSI reference model (X.200), and work by exchanging predefined messages.