Mobile Ring Indicator

[kluivert]

I am doing my project in GSM car alarm and i need to activate the system by a phone call from the car owner.

I found Pin 9 RI in the serial port is ring indicator it may be very useful for my idea but i am using Siemens SL55 and i found that this pin 9 is useless as it gives no signal when i call the mobile.

Do this pin needs activation from AT command ? or what ?

Thanx in advance

 

[Maddogg6]

https://en.wikipedia.org/wiki/Ring_Indicator

The asserted RI signal lasts nearly exactly as long as the ringing on the telephone line - for example, 2.0 seconds per ring burst in North America. The RI signal follows the ringing pattern closely - in fact, it is possible for a computer program to detect distinctive ring patterns from the phone company by monitoring the transitions of the RI signal. If the phone line rings, for example, two short burts and then a long burst, the RI signal will imitate this pattern

So - its supposed to be an output of the modem - right?

If you are absolutely sure there is no activity on that pin..(??) .. its possible to use software.
That pin was designed to cause an interrupt on a PC (Phone is ringing...or for auto answer)

In such a system, maybe interrupts were not employed as in PC's..?? (other source of interrupt, like in software upon receiving other serial data from the modem..??)

Also, if its a 'security system', they *could* have also changed things around (pin 9 <> RS232 PIN9) - aka 'security layer via obfuscation'

 

[kluivert]

The RI pin9 is floating and useless so what should i do instead , i have an idea to check "R I N G " characters sent by the mobile is this right

thanx for ur help