I had a power outage in my business location last week and all my three inter-tel phones + At&t cordless phone (with answering machine) stop ringing. I followed one of the instruction from this forum (For line ring programmig, go to the side of your GLX cabinet and put the toggle switch to "program", then go to the phone you want to ring and (with handset in craddle) dial #2 (pound 2) then press the line buttons that you want to ring. Lift up handset and hangup, you should hear conformation tone. Thats it.)
and i got my ring back in all corded phones but how can i program my AT&T cordless phone ( it was working before the power outage,when any of the phone line rings my cordless phone used to ring with it and if i miss the call the answering machine attached with this phone used to record the message ) so i can use my answering machine and cordless feature one more time.
Appreciate your help.

I honestly cannot remember connecting a S/L set to a GLX, unless it was connected to the DATA port on an executive key set. Is the S/L connected to a keyset?

But then if you have a Inter-tel GLX-Plus:

Lift the handset
Enter the CO line access code(s) that are to ring.
Hang up

If you have the manual the instructions are on page 5-13 paragraph 5.8

Dean, good memory. If you don't know which 1 you have, if you have display sets it's GLX plus.

Btw, one of the best SMB systems made.

Thanks for your reply. I found the manual online . Where can I find access codes. I am using GLX PLUS with display set.
This system was installed long time ago. Appreciate your help.

In the manual page 4-18. Section 9.3 To place an outside call then, Single-line set:

The AT&T Cordless is not recognizing the line and there is no tone at all. After the power surge I lost the communication between GLX Plus and Cordless phone. Therefore, I am unable to receive Voice Mail Messages or calls on Cordless. I think I made it even worst since before at least I was getting a busy tone on Cordless now it's complete silence. Please advise!

In the manual page 6-14, FIGURE 6-5. SINGLE-LINE SET TROUBLESHOOTING CHART
This will point you in the correct direction as to solving the problem.