Configuring a Call Prefix

A call prefix is a string of consecutive digits starting from the first digit of a called number. It can be the first digit or several digits starting from the first digit of a called number. That is, a call prefix is a subset of a called number. For example, you can define either of the following intra-office call prefixes for the called number 1234:

• First digit: 1
• First two digits: 12
• First three digits: 123
• Called number: 1234

A group of call prefixes configured on the PBX constitutes a DN set. If the preceding call prefixes all exist in the DN set, the PBX analyzes the called number according to the longest match principle. For example, a user calls 1234. If call prefixes 1, 12, and 1234 are configured in a DN set, the PBX matches the called number with the call prefix 1234 according to the longest match principle.

Call prefixes are classified into the following types:

• Intra-office call prefix: is applicable to scenarios where intra-office and inter-office users call intra-office users. For example, the intra-office number range is 7000 to 7099. You can configure the intra-office call prefix 7. You need to dial only the intra-office user number such as 7001 when calling an intra-office user.
• Inter-office call prefix: Inter-office call prefixes are used by intra-office users to make outgoing calls, for example, intra-office users make local calls, national toll calls, and international toll calls. Assuming that the inter-office call prefix is 9, intra-office user 7000 can dial 912345678 when calling inter-office user 12345678. The PBX parses and changes the number (for example, delete 9) to make outgoing calls, as shown in Figure 2-15.
  Figure 2-15 Inter-office call
  

A call prefix can be flexibly configured, and depends on the user number plan.

It is recommended that you configure prefixes for intra-office, local, national toll, and international toll calls. By default, even if the national and international toll call prefixes are not configured, the system automatically determines whether a call is a local, national toll, or international toll call according to the number a user has dialed. If the user does not have the corresponding call rights, the system denies the call. If a user has the requirements to make national or international toll calls, configure the national (ddd) or international (idd) toll call rights.

The 214 control point enables or disables automatic determination and call restriction functions, and it does not affect the call restriction functions when national and international toll call prefixes are configured.

In the tandem scenario, if the outgoing prefix of PBX2 is the same as the country code prefix or area code prefix of PBX1, users under PBX1 need to dial the outgoing prefix (for example, 9) of PBX1, outgoing prefix (for example, 0) of PBX2, and then a user number, which is 90+user number, and one digit of the called number needs to be deleted on PBX1. Figure 2-16 shows the trunk tandem network. Assuming that the country code prefix is 00 and area code prefix is 0, if a user under PBX1 has only the right to make local calls, the user cannot make outgoing calls by dialing 90+user number. This is because PBX1 considers 0+user number as a toll call number. When the national and international toll call prefixes are not configured, configure the 214 control point so that the system will restrict calls not according to the calling parties' call-out rights. For details, see pbx number-parameter.

Figure 2-16 Trunk tandem network

If the 214 control point is configured for the system to restrict calls not according to the calling parties' call-out rights, toll fraud may occur. In this case, the national and international toll call prefixes must be configured to prevent toll fraud.

Set the intra-office call prefix to 7 and inter-office call prefix to 9.

<Huawei> system-view
[Huawei] voice
[Huawei-voice] callprefix 7
[Huawei-voice-callprefix-7] prefix 7
[Huawei-voice-callprefix-7] call-type category basic-service attribute 0
[Huawei-voice-callprefix-7] digit-length 3 4
[Huawei-voice-callprefix-7] quit
[Huawei-voice] callprefix 9
[Huawei-voice-callprefix-9] prefix 9
[Huawei-voice-callprefix-9] call-type category basic-service attribute 1
[Huawei-voice-callprefix-9] digit-length 1 15
[Huawei-voice-callprefix-9] save