Handshake failure with Portugal Telecom SMS center

[Tech Support]

Unfortunately the 'two chirps' you describe still doesn't sound like a modem on the other end. The carrier signal from the remote modem should be long and steady (at least 3 seconds or so). I still think you aren't getting through to the other modem.

[RACameron]

Siemens technical support provided some information. Apparently on Portugal Telecom's fixed-network SMS service, the number listed as a service center (manual, PT tech support and screen of cordless phone) does not provide a modem tone.

Exactly how the connection can be made under these circumstances was not clearly explained. When I try to listen on an extension to hear what is going on, the process fails and reverts to a busy signal. I hear modem tones from the phone but only 'chirps' from the service center.

Unfortunately, this makes it impossible to use your very fine software. Eventually someone else will run into the same problem and an answer will be found. Please reply at that time, or as soon as you have any other ideas.

[RACameron]

I have found references saying that FNSMSC's (Fixed Network SMS Centers) operate with FSK (Frequency Shift Keying) modulation, at 12KB. Am I correct, this is different from the phase-shift modulation used by the more-common mobile SMS gateways?

According to information in the Windows Modem control panel (advanced options) it is necessary to match the modulation of sending and receiving modems or the communication will fail. There is an option here for selecting the older, Bell-type of modulation. (The code it inserts may not be correct, B0 vs. B1, but this is another matter.)

NotePager 32 does allow a selection of Hayes AT command strings, but unfortunately all include the command &F, which, if I am correct, will reset the modem to the factory default of phase-shift modulation everytime the string is sent, no matter what has been selected in Windows. It is my understanding the modem always gives preference to the last-sent AT string, no matter what was previously set, and I assume NotePager sends the string immediately before each message.

Attempts to alter the command string sent by NotePager 32: I have found that no matter what I enter into the top of the NotePager drop-down modem command menu in Carriers->Edit, it always defaults to one of the pre-determined strings, all of which begin by returning to modem to factory default settings. Your comments and assistance will be appreciated.

[RACameron]

Ouch! The connection speed, of course, should have been 1200 baud, not 12 kb. I am looking forward to your reply on how to try a connection with the FSK protocol. I am hoping to at last get a connection. I hope FNSMS uses the same data format as mobile SMS.

[RACameron]

First, I can see from reviewing this thread, I neglected at the outset to specify the make and model of my modem. In reviewing previous posts, most of your successful attempts to help users get through to their service centers start with your knowing this information.

Second, I may have moved the discussion in the wrong direction with my concern that NotePage32 was continually resetting the modem to phase-shift modulation, once I found out that fixed-network SMS's usually run with Frequency Shift Keying modulation. On more careful reading of the supplied AT command strings I see that two or three of them [i]do[/i], in fact, turn on the FSK modulation, later in the string, with the B1 command.

Perhaps it is best that I start a new thread or the resulting post will become too long and confusing to help other users who may have the same problem. Then, when a new and more brief thread (hopefully!) leads to a successful conclusion, you may wish to delete this one.

[Tech Support]

I will reply in your new thread