NETGEAR XM128 ISDN manual Answering a V.120 Call, Making a V.120 Call

Reference Guide for the Model XM128 ISDN Digital Modem

Answering a V.120 Call

In most cases, there is no need to configure the Model XM128 modem to properly answer calls. The Model XM128 modem decides which protocol to use by detecting the type of data that is received. You only need to set S0 to greater than or equal to 1 in order for the modem to automatically answer an incoming call. If S0=0, the DCE simply reports RING to your terminal and sounds a ring notification.

One exception to this is when the ISDN data call is carried through speech bearer. In this case, you would need to make an MSN entry for the phone number from which you are expecting the data-over-speech-bearer call to be coming. For V.120 protocol, use AT&ZI2=n. Refer to “Data over Speech Channel” on page 6-7.

Making a V.120 Call

Some switches transmit all network signals through the D channel (out-of-band signaling), allowing both B channels to be used exclusively for your communication purposes. This arrangement allows for throughput of 64 Kbps per channel. However, not all switches support out-of-band signaling at this time. For switches that do not support out-of-band signaling, network signals are transmitted through the B channels, which reduces the bandwidth to 56 Kbps.

When making a V.120 call, be sure that the communication supports out-of-band signaling. If it does not support out-of-band signaling, you need to set your Model XM128 modem to 56K mode using the AT&E1 command (AT&E0 to set it back to 64K mode). If your modem is on the receiving end, you can keep the setting at AT&E0 (64K data mode). The modem automatically switches between the two speeds in answer mode.

Configuring the V.120 Mode

To configure for a 56K V.120 call, use the following commands:

1.Enter ATB20 (Select V.120 for communication).

Model XM128 modem should respond with:

OK

2.Enter AT&E1 (Select 56K data mode).

Model XM128 modem should respond with:

OK

6-12 ISDN Overview