I have a Simon XT (v.1.2) in a remote location that I've accessed remotely via telephone many times over the course of about 3 years to check the status or arm/disarm it. A few months ago I was no longer able to control the panel remotely. It picks up, prompts for the access code, and then either goes silent or the modem tones start.
This is the same way the panel would respond if you supplied an invalid access code. However, I've confirmed the panel is still expecting the access code I am supplying by having someone disarm the panel using the access code directly on the panel. (I've also tried remotely using the dealer and installer access codes, in addition to the user access code, even though I know it should be looking for the user access code. None worked.)
So if the code is correct, is the phone bad? I tried a few different phones on different lines. No change.
Is the touch-tone decoder on the panel broken? It seems to work - at least minimally - as it responds correctly when the panel makes an outbound call and prompts the user to enter * and # to cycle through the status reports. Also, at least some of the time when the panel is called it halts playing its prompt in response to hearing the access code, so it is catching at least some of the digits.
The Simon XT tone decoder has always been slow to respond (easy for it to miss digits if you hit keys quickly), so I made sure to use an analog, land-line phone that outputs tones as long as you hold keys, and several times tried entering the access code while holding each key for 1/2 to 1 second. It didn't help.
Anything else worth trying?
Anyone else see this failure scenario with a Simon XT?