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This chapter describes how to make calls using the VTA. It covers the following topics:
After the room system is connected to the VTA, the VTA is connected to the LAN, and both the room system and the VTA are up and running, use the room system dialer to make your call.
In all cases, the bandwidth of the calling room system (via the VTA) must be the same as the bandwidth of the receiving endpoint (gateway, VTA, H.323 terminal, or H.320 terminal). This means that before you call:
In a basic call, the default bandwidths of both the calling and the receiving units are the same. However, there are cases when you must change the default bandwidths of the calling VTA or the receiving VTA, or both. You can do this by adding a dialing prefix (to change the outgoing bandwidth) or a dialing suffix (to change the receiving VTA's incoming bandwidth).
When the bandwidth of the calling VTA is the same as that of the receiving unit, dial the extension or phone number of the unit you're calling. Several basic dialing examples are described as follows.
When the calling VTAs and the receiving endpoint are on the same LAN segment and set to the same default bandwidths, simply dial the extension of the endpoint you are calling (see Example 6-1).
5555
Where 5555 is the extension of the endpoint you are calling.
When you are dialing through a gateway to an H.320 unit, you must take into account not only the bandwidths of the calling VTA and the receiving unit, but the bandwidth of the circuit switched network that connects the two sides (Example 6-2).
If:
then you do not have to change the bandwidth. You must, however, dial:
Step 1 The gateway's service prefix, followed by
Step 2 The first channel phone number, followed by
Step 3 The second number delimiter.
Step 4 If the second channel phone number is different from the first, you must dial that number after the second number delimiter; if it is the same as the first, do not dial it.
80 7654321*
Where 80 is the gateway service prefix, 7654321 is the phone number of the both first and second channels of the unit you are calling, and * is the second number delimiter (Example 6-3).
80 7654321*7654322
Where 80 is the gateway service prefix, 7654321 is the phone number of the first channel of the unit you are calling, 7654322 is the phone number of the second channel, and * is the second number delimiter.
When you are dialing through a gateway and an IMUX to a unit that has the same bandwidth as the calling VTA, dial:
Step 1 The gateway's service prefix, followed by
Step 2 The IMUX profile, followed by
Step 3 The phone number of the receiving unit; if this is a 2x64 kbps call, this will be
80 #001 7654321*
Where 80 is the gateway service prefix, #001 is the IMUX profile, 7654321 is the phone number of the both first and second channels of the unit you are calling and * is the second number delimiter. (You do not have to dial the phone number twice because the phone numbers are the same for both channels.)
When you are dialing through a second gateway to an H.323 endpoint on a remote LAN, if:
then you do not have to change the bandwidth. You must, however, dial:
80 7654321 (IVR prompt) 6666
Where 80 is the gateway service prefix, 7654321 is the phone number of the second gateway, and 6666 is the extension of the remote unit.
When you make a call, it is transmitted from the calling VTA at the default outgoing bandwidth, which is set during VTA configuration; however, if the endpoint you are calling is set to a different bandwidth, or if you must go through a gateway which requires a different bandwidth, you can change the default bandwidth of the calling VTA by adding a prefix to the dialing stream.
To make a call, the bandwidth of the calling VTA must match that of the called endpoint. When default settings do not match, you can force a change in the bandwidth of the calling VTA.
There are three instances when this is necessary:
Add the prefix before the dialing stream to force a change in the bandwidth of the VTA that is calling.
Table 6-1 displays the prefixes that you dial to force a change in the outgoing bandwidth (note the difference between prefixes for non-restricted and restricted bandwidths):
| To Force Calling Bandwidth to: | Use Prefix: |
2 x 64 kbps (2B) | #00 |
128 kbps | #10 |
384 kbps | #20 |
2 x 56 kbps (2B) (restricted) | #01 |
112 kbps (restricted) | #11 |
336 kbps (restricted) | #21 |
Several outgoing bandwidth dialing examples are described in the following sections:
When the calling VTA is set to 384 kbps, and the receiving unit is set to 128 kbps, dial:
#10 3333
Where #10 is the prefix that forces the calling VTA's bandwidth to 128 kbps and 3333 is the extension of the receiving endpoint.
When the calling VTA is set to 384 kbps but the call is sent at 2x64 kbps through the gateway to the remote H.320 terminal, dial:
Step 1 The dialing prefix, followed by
Step 2 The gateway service prefix, followed by
Step 3 The first channel phone number, followed by
Step 4 The second number delimiter;
Step 5 If the second channel phone number is different from the first, you must dial that number after the second number delimiter; if it is the same as the first, do not dial it (see Example 6-7 and Example 6-8).
#00 80 7654321*
Where #00 is the dialing prefix, 80 is the gateway service prefix, 7654321 is the phone number of the both first and second channels of the unit you are calling and * is the second number delimiter.
#00 80 7654321*7654322
Where #00 is the dialing prefix, 80 is the gateway service prefix, 7654321 is the phone number of the first channel of the unit you are calling, * is the second number delimiter and 7654322 is the phone number of the second channel.
When you are calling through a gateway and an IMUX to a unit that has a different bandwidth, dial:
Step 1 The dialing prefix, followed by
Step 2 The gateway's service prefix, followed by
Step 3 The IMUX profile, followed by
Step 4 The phone number of the receiving unit; if this is a 2x64 kbps call, this will be
The calling VTA is set to 384 kbps but the receiving unit is set at 128 kbps; dial:
#10 80 #001 7654321
Where #10 is the prefix that sets the bandwidth to 128 kbps, 80 is the gateway service prefix, #001 is the IMUX profile, and 7654321 is the phone number of the remote unit.
When making calls between two VTAs, you can force the VTA receiving the call to change its default bandwidth to match the bandwidth of the VIU-323 making the call.
To do this, add a dialing suffix after the phone number of the remote VTA. Dialing suffixes are for nonrestricted bandwidths only and are described Table 6-2:
| To Force Receiving Bandwidth to: | Use Suffix: |
2 x 64 kbps (2B) | 0 |
128 kbps | 1 |
384 kbps | 2 |
During VTA configuration, you enter the VTA's phone number in the Network Parameters screen. This phone number is registered with the gatekeeper (whose IP address is entered in the same screen). The VTA's phone number is registered in the gatekeeper as four aliases; three of these are the original number with a suffix added, for example, if the phone number is 5555, the gatekeeper adds the suffixes 0, 1 and 2 so that:
For a call to succeed, the bandwidth of the called VTA must match that of the calling unit, but this does not always happen. When the bandwidth settings do not match, you can force a change in the bandwidth of the receiving VTA. There are three instances when this is necessary:
Add the suffix after the dialing stream or when prompted, for example, by the Gateway's IVR (Interactive Voice Response).
When an H.323 endpoint calls a VTA, within a LAN and the receiving VTA is set to a different bandwidth:
Step 1 Dial the extension of the receiving VTA.
Step 2 Dial the appropriate dialing suffix (see Example 6-10).
The calling endpoint is set to 384 kbps but the receiving VTA is set at 128 kbps; dial:
7777 2
where 7777 is the receiving VTA's extension and 2 is the suffix that changes the incoming bandwidth of the receiving VTA to 384 kbps.
If the bandwidth of the calling VTA is 2x64 kbps and the receiving VTA's bandwidth is 384 kbps, dial:
Step 1 The first gateway's service number, followed by
Step 2 The phone number of the remote gateway.
When you are prompted by an IVR message (for example), dial:
80 7654321 (IVR prompt) 4444 0
Where 80 is the service prefix of the first gateway, 7654321 is the phone number of the remote gateway, 4444 is the extension of the remote VTA, and 0 changes the receiving VTA's bandwidth to 2x64 kbps.
In some cases, you must dial both a prefix and a suffix. Because the network sets bandwidth availability at any particular time, you may have to use lower bandwidths during peak hours. You may therefore have to use a prefix to force the outgoing call to a lower bandwidth and a suffix so that the VTA you are calling can receive the call. Remember that you can only use a suffix when calling from one VTA to another.
If both VTA's are set to 384 kbps, but the call doesn't go through, send the call at 128 kbps by dialing the following:
#10 80 7654321 (IVR prompt) 4444 1
Where #10 changes the calling VTA's bandwidth to 128 kbps, 80 is the service prefix of the first gateway, 7654321 is the phone number of the remote gateway, 4444 is the extension of the remote VTA, and 1 changes the receiving VTA's bandwidth to 128 kbps.
Posted: Fri Nov 12 19:49:10 PST 1999
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