Administrator Guide: DAHDI

Table of contents

Channel calculations

Each type of card and configuration requires a certain amount of channels to be configured. The information below outlines how many channels each type of interface provides and how to calculate the channel usage.

Sangoma BRI and PRI Channel usage

Physical card	Usable DAHDI channels	DAHDI channels consumed
Sangoma BRI	2	3
Sangoma PRI E1	30	31
Sangoma PRI T1	23	24

A single BRI interface has 2 B-channels (bearer channels) that can transport audio/voice, and one D-channel that transports signaling. That's a total of 3 channels per BRI interface. The first 2 channels are the B-channels, the last channel is the D-channel.

A PRI E1 interface has a total of 31 channels. The 16th channel is used as a D-channel. The first 15 and last 15 channels are hence used as B-channels. A PRI T1 interface has a total of 24 channels. The last channel is used as a D-channel. The first 23 channels are hence used as B-channels.

When calculating the DAHDI channels used for your interface, keep in mind that the channel counting starts at the first card. If for example you have a 2 PRI card, the first channel of the first interface is 1 and its D-channel is 16. For the second interface the first channel is 32 and its D-channel is 47. Similarly, if you have a 4BRI card and a 1PRI card in the same server, the first channel of the 1PRI card will be 13, its D-channel will be 28 and its last channel will be 43. All this depends on the order you selected in the Sangoma Card support module.

Troubleshooting

You see an alarm on the card and no calls are possible.

Have a look on the wikipedia page about alarms. The alarm type should indicate where the issue is located.