# Call Recognition Service

## Description

Call Recognition Service (CRS) checks the calling line ID of the incoming call to determine whether the caller is an external hot desk user (EHDU) and whether the trunk is "trusted" or "non-trusted." If the caller is an EHDU on a trusted trunk, he or she is automatically logged in. The digits dialed by the EHDU are then processed and the call routed to the intended station or other destination. If the digits terminate on the Hot Desking Access Number, then the user is provided dial tone and may continuing dialing.

A non-trusted EHDU must enter his or her PIN to log in. Without CRS, the EHDU would have to dial the Hot Desking Access number followed by their hot desk user directory number and User PIN to log in (unless they have "Permanent Login" enabled in their Class of Service).

CRS also provides integration with the Closed User Group (CUG) services (also known as Force-to-PBX or its abbreviation, FOPBX) offered by some mobile phone carriers. With CUG, all calls to, or from, a mobile subscriber are routed to a PBX over a dedicated trunk for processing. When used in conjunction with EHDU, the PBX can recognize calls made from mobile devices as originating from an EHDU by matching the PSTN number of the device to its EHDU directory number. To recognize that a call is being made to the mobile phone, the PBX matches the called party number (i.e., the PSTN number of the mobile phone) with the EHDU. Once recognized, the PBX substitutes the PSTN number with the EHDU directory number and routes the call to the EHDU. And since the PBX is always in the call path, it can maintain device state (busy, idle, call forwarding active, etc.) and offer mid-call features through DTMF detection.

NOTE: The Hot Desk Access Number is still required even with CRS since not every internal destination will have an associated DID number. Also, EHDUs who aren't members of a CUG need to connect to the number to make external calls or use system features.

### Summary of CRS Treatments

CRS works by looking at the digits received on a trunk and the CRS mark assigned to that trunk. The two together determine the treatment the call gets—i.e., whether the caller is required to enter a PIN and whether the system looks at the calling and called party numbers when it attempts to match the digits to an EHDU.

CRS Mark | PIN Required? | Numbers to Match (see Notes)
Off | No | None
EHDU trusted | No | Calling Party
EHDU non-trusted | Yes | Calling Party
Force to PBX (FOPBX) trusted | No | Calling AND Called Party
Force to PBX (FOPBX) non-trusted | Yes | Calling AND Called Party

NOTES

1. Matching is attempted only after any incoming digit modification is applied. If CRS fails to match any numbers, the call gets normal treatment.

2. The called party number must contain all the EHDU external digits (as configured in the User and Services Configuration form) for CRS to find a match.

   Called Party Number | EHDU External Digits | Match?
   6135925555 5925555 0016135925555 | 6135925555 6135925555 6135925555 | Yes No Yes

### Examples of EHDU Recognition

The following examples illustrate the value of CRS by comparing how it effects EHDU operation in nodal and networked environments.

A) Nodal EHDU without CRS

John is an EHDU. He wants to call into the system to retrieve his voice mail messages. First, he logs in by dialing the EHDU Access Number, followed by his internal directory number and PIN. The system responds by returning dial tone. John then dials the voice mail hunt group number. Seeing that the call is from an internal extension, the voice mail system welcomes John to his mailbox and prompts for his password.

B) Nodal EHDU with CRS

With CRS, to retrieve his messages John dials the voice mail DID number. The call is present to the system with John's PSTN number. The trunk is configured to trust EHDUs so John is automatically logged in and routed directly to voice mail. The voice mail system then welcomes John to his mailbox and informs him of the number of messages he has waiting. No voice mail PIN is required as John is considered an authorized user.

C) Network EHDU Recognition with CRS

Michelle works for a company with offices in New York City and Chicago, each with its own cluster of MiVoice Business systems. The clusters are networked. EHDU data is shared between both locations but each has its own Hot Desk Access Number. When Michelle is in New York (her home node) and wants to connect to the local cluster from her mobile phone to make an outbound call, she dials the New York Hot Desk Access Number. In Chicago, she dials the Chicago Hot Desk Access Number to access the cluster there.

When Michelle is in Chicago and wants to call an internal extension or PSTN number in New York, she simply dials the local (Chicago) Hot Desk Access Number and is recognized as a trusted EHDU. Her call is then routed over network trunks to the New York office based on the PNI
See Primary Node Identifier. prefix in her EHDU DN. She is then given dial tone from the New York PBX and can now make local calls without incurring long distances charges.

She could save even more by using EHDU Callback service which takes advantages of the reduce charges applied by most North American mobile carriers on incoming calls.

## Conditions and Feature Interactions

- CRS is supported on any trunk that delivers calling number. These include: PRI, DASS, BRI, TDM DPNSS, SIP, QSIG, ANI/DNIS delivery trunks, and LS Class.

- Mobile carriers that offer CUG service prefix all called party numbers with certain a digit string. Each carrier uses a different prefix that must be absorbed (deleted) from the dialed number when they arrive since they would interfere with CRS. See ARS Digit Modification Plans for more information on setting up incoming digit modification.

- When PSTN gateways are used, the DID digits received must translate to a recognized destination on the gateway performing the CRS matching. If the calling party number is matched to a remote directory number, the originally dialed number is saved and processed on the EHDU’s home node. These digits must translate to a valid destination on the EHDU's home node or else the call will be rejected. If the incoming DIDs map to speedcalls on the PSTN gateway, you can facilitate translation by sharing the speedcalls within the network.

- To provide CRS capability from a trunking gateway to multiple standalone nodes or clusters, CRS data must be SDS-shared from each individual node/cluster to the trunking gateway.

- If the calling party number translates to a Hot Desk Access number on the PSTN gateway, it is the gateway, not the EHDU's home node, that validates the PIN and returns dial tone.

- Many mobile carriers will not send the * and # digits in the calling party number. If there are feature access codes in the system that contain these digits, alternate codes that contain only digits 0-9 must be provisioned. Care must be taken to ensure that the alternate codes do not introduce dialing conflicts.

- When the mobile phone user dials the public emergency number (e.g., 911), the call is NOT forwarded to the PBX for handling. Instead, it is intercepted by the mobile carrier and handled accordingly.

- Trusted EHDUs who have mailboxes and call the embedded voice mail system to retrieve messages bypass the usual mailbox login procedure (PIN entry).

- If both the CRS and the Direct Inward Dialing (DID) Service are enabled (see Trunk Attributes form), a rare conflict scenario can occur where FOPBX is configured as the CRS option and the EHDU external number matches the DID number. In such cases, the call will be handled by the CRS and not the DID Service.

- If an EHDU invokes a DID call (DID number hosted by its home node), both CRS and DID services will be applied to the call.

- The Caller Based Routing uses the CRS feature for call routing. However, there is no impact on the incoming digit modification of the trunk attributes, as the Caller Based Routing feature uses the CLI rather than the dialed destination.

## Programming

1. Trunk Attributes form

- Enable Call Service Recognition on an unused Trunk Service number.

2. Analog Trunks form ( ), Digital Trunks form ( )

- Assign the above Trunk Service number to trunks handling EHDU calls.

3. ARS Digit Modification Plans form

4. Set up incoming digit modification to absorb digits received from mobile carriers as required.

For EHDU programming, see External Hot Desking - Programming.

## Device Support

Call Recognition Service is available to external hot desk users only.

## Operation

None

Related Topics

- External Hot Desking - Description

- External Hot Desk User Callback

- Call Recognition Service form

- CRS QUERY maintenance command