State of two ISDN

I have a problem that i’m sure you can help me solve.

We have 2 phone line number (ISDN), that are redirected to an internal sip (an extension).
While 1 ISDN is busy, we can use the other to make/receive calls from the extern, but when both line are busy, we can’t make/receive calls from the extern.

It would be nice if we could know the state of the ISDN (busy or free), to know if we can make call to the extern.

We’re using Yealink T28P SIP, and i would like to have 2 (or either 1) led, to know the status of the phone lines, red if busy, green if free.

How could i set that in Asterisk?

I was thinking of a state that is communicate to the phone and they alter the led as the status change.
Thanks for the help, hope to receive good news soon

Best Regards

I haven’t tried a case to use Device state with ISDN but in that case you can use Custome device state and Hint for your purpose. … +and+Hints

–Satish Barot