3Com V7122 User Manual page 27

The number of total and free channels is published in a 200 OK response to an
OPTIONS request. The gateway uses the X-Resource header in the following format:
'X-Resource: telchs=100/240;mediachs=0/0',
Where 'telchs' specifies the number of free tel channels / total tel channels.
For more updated information on the gateway's supported features, see the latest V7122
Gateway Release Notes.
V7122 Gateway User Guide
27