Digital Call Forwarding and Digit Manipulation

The figure below shows the flow of dialed digits between two digital telephone installations within the Passport network. Each node is equipped with an E1 Voice Module (EVM) and two digital Voice Expansion Modules configured with an aggregate of 30 digital voice module channels arranged in a hunt group.

Example 1

The user connected to a station of the Los Angeles PBX attempts to reach PBX station 53456 in New York. To do that, he first dials trunk access code 7. Following receipt of a dial tone from the first available DVM voice channel in the Passport 4400 hunt group, he dials 21253456. One of the ingress numbers provisioned in the Los Angeles ingress table is 2125****. Based on this ingress number, the digits forwarded to the New York node are 21253456.

At the New York node, some of the digital voice channels, whose phone numbers match digits 2125****, are indexed for manipulation string D3*****. As a result, the first digital voice channel matching 2125**** will drop 212, and forward digits 53456, ringing that PBX station. The call is established when the party at station 53456 answers.

Note: After completing the call, you must wait a minimum of five seconds before attempting to make another call over the network. Otherwise, you will receive a fast busy signal. The five-second delay compensates for latency inherent in the network. It also allows the PBX to distinguish between a true on-hook condition and a momentary flash-hook used to transfer a call, placing the call on hold, or similar switching action.

Example 2

The user connected to a station of the Los Angeles PBX is attempting to reach a party in the New York area whose telephone number is 7511234. To do that, the caller dials 7, then 21207511234. One of the ingress numbers provisioned in the Los Angeles ingress table is 2120*******. Based on this number, the digits forwarded to the New York node are 21207511234. At the New York node, some of the digital voice channels whose numbers match 2120 are indexed for manipulation string D4I9+*******.

As a result, the first digital voice channel matching 2120 will drop 2120, forward digit 9, wait one second (long enough to obtain a dial tone from its PBX), then forward digits 7511234. The call is established when the party at 7511234 answers.

Note: If the number of digits dialed by the user exceeds 7, as is the case in the two examples above, make sure that the maxNumFwdDigits profile parameter was previously set to a value of 8 or higher (default value is 7). Otherwise, the voice channel will stop collecting digits beyond 7, and no match will ever be established. To change the maxNumFwdDigits to a higher value, see Maximum Number of Forwarded Digits.

The figure below shows a mix of digital and analog telephone installations within the Passport network. Here a Passport 4430/50/55 unit at Node 2 is configured with an E1 Voice Module (EVM) that includes six Digital Voice Modules (DVM) B1 through B6 in location B, and a dual channel Analog Universal Voice Module (AUVM) in location C.

The six DVMs are configured with extension numbers 121 through 126, respectively, and are logically connected over an E1 line to a digital PBX. Connection to the E1 line was previously established with the command CLI>set t1e1 ds0Connect.

Of the two analog voice channels in the AUVM, C1 is equipped with an FXS interface module configured with network extension number 131, and connected to an analog telephone. Analog channel C2 is equipped with an FXO interface module configured with network extension number 132, and connected to station 5678 of an analog PBX.

At the Node 1 end, the first three entries in the ingress table contain the ingress numbers associated with the Node 2 egress table.

Example 3

Assume that the user at Node 1 wants to contact station 2345 of the digital PBX at Node 2. To do that, he dials the trunk access code, then 1252345. The digits 12* are used by the Voice Network Call Server (VNCS) to identify the destination of the call as Node 2. Based on ingress number 12*#, all seven digits are forwarded to Node 2. Here, 125 directs the call to DVM B5. As noted before, DVM B5 was previously connected to one of the E1 channels, possibly DS0 5 or any one of the remaining 29 channels.

Consulting the Node 2 egress table, the manipulation string of index 5 is D3#.

Note: The # sign is needed to insure that the remaining digits, whatever their number, are to be forwarded to the PBX. If a 4-digit numbering plan is used, the manipulation string could be changed to D3****.

As a result, the digits 125 are dropped from the string, and the remainder, digits 2345, are forwarded to the digital PBX, ringing station 2345. Besides station 2345, the user may access any other station on the digital PBX, or go off net via the PSTN connection, by dialing the appropriate combination of trailing digits instead of 2345.

Summary for example 3

Example 4

To contact the analog telephone connected to FXS voice channel C1, the user at Node 1 would dial the trunk access code, then 131. The digits 13 are also resolved to Node 2. Subsequently, digits 131 are forwarded to analog FXS channel C1, ringing the attached telephone. Note that there is no manipulation string associated with index 7 in the Node 2 egress table, since this telephone is the final destination.

Summary for example 4

Example 5

To reach a station, such as 5685, on the analog PBX of Node 2, the user at Node 1 would dial the trunk access code, then 1325685. Following address resolution, the digits 1325685 are forwarded to analog voice channel C2. This channel is physically connected to analog PBX station 5685. Based on the manipulation string associated with index 8, the digits 132 are dropped, and digits 5685 are forwarded to the PBX, ringing station 5685. As in the digital case, the user may access any other station on the analog PBX, or go off net via the PSTN connection, by dialing the appropriate combination of trailing digits instead of 5685.

Summary for example 5

End of Topic