6/23/2009 9:26 AM | |
Posts: 173 Rating:
|
PSTN / POTS / Fixed line Teleservice =========================== This was shown possible with the LOGO! in October 2003 for the 0BA4 (see in the zip file). It gives some clues about the communication (cross over Tx & Rx means modem DCE to LOGO! DTE communication, and the AT command settings for the modem also give some more info). This 'procedure' has been replaced with the Modem Cable and Wizard in Soft Comfort V6, but essentially, it is still the same - check the COM port settings and also if you check the Modem cable with a multimeter. Teleservice over GSM ================ OK - this is a long outstanding topic. Here I will give some of the info that I have found and hope that someone else can add some more detail or experiences. I have been looking for a solution to this problem for the past 4 years (off and on) and below are the 3 difficulties that I have come across. 1) 11 bit GSM modem This is the reason always given, but I think that the other 2 aspects are also a problem. Most GSM modems only support 10 bit 'character framing' of 8N1 or 7E1 (1 Start bit, 8 Data bits, no parity, 1 Stop bit OR 1 Start bit, 7 data bits, EVEN parity bit, 1 Stop bit). Some of the modems you can send an AT command to it (via hyperterminal or in an initialisation string) to change this configuration. Some GSM modems even allow 11 bit communication on the RS232 side (PC & LOGO! side) even if the communication between 2 modems over the GSM network is 10 bit. There are many manufacturers of modems in the world, but most of them use the 'wireless module' or 'cellular engine' compnent from one of the following manufactureres 2) Synchronous vs Asynchronous communication Synchronous communication requires some extra connection lines for 'handshaking' so that the 2 sides can synchronise 'clocks' and so that one side knows when data is coming from the other side and when to determine the value/status of a bit (0/1, on/off). With Asynchronous, one side sends, and the other 'works-out' the speed/pace/flow of bits, without a synchronised transfer. (search for "synchronous vs asynchronous" on google for the definition on Wikipedia fo in-depth info under the discussion page. I have included what I think is important in the zip document)So from the adaptor wiring, it looks like there is ASYNCHRONOUS communication, but the modem AT command settings confuse things again. - see zip document 3) Transparent vs non-Transparent data What this essentially means is that the GSM network's IWU will add special error correction codes to control the flow of data. If there is no such acknowledgement signal from the receiver, the networks will utilise their "data buffering" feature by using a special "forward correction" technique to ensure uninterrupted data transmission throughout. Not all cellphones support GSM's Non Transparent (RLP-based) data capabilities.
Non-Transparent data only applies to data transfers and not faxing since the Group 3 standard for fax transmission is a transparent protocol AttachmentTeleservice.zip (883 Downloads) |
Last edited by: CS Moderator at: 6/25/2009 7:57 AMnew subject after splitting |
|
This contribution was helpful to
1 thankful Users |
Follow us on