i need copy of AT commands for siemensc35

"The main problem with using a normal phone, is that there is no easy way to turn them on/off"

Yes, that's true - but I wouldn't say it's the main problem.

I think that the main problem with using a phone is that the interface is likely to be undocumented and unsupported - they are sold, supported and documnted for consumer use as telephones.

So, if you do want to use a phone, you must be prepared to put in the effort to "reverse engineer" it. The phone may be "free", but this is the "hidden" cost!

A GSM modem or module, on the other hand, is specifically designed for this type of application - with appropriate interfaces, documentation and support.

Used GSM modems are fequently available quite cheaply on ebay.

"The main problem with using a normal phone, is that there is no easy way to turn them on/off"

Yes, that's true - but I wouldn't say it's the main problem.

I think that the main problem with using a phone is that the interface is likely to be undocumented and unsupported - they are sold, supported and documnted for consumer use as telephones.

So, if you do want to use a phone, you must be prepared to put in the effort to "reverse engineer" it. The phone may be "free", but this is the "hidden" cost!

A GSM modem or module, on the other hand, is specifically designed for this type of application - with appropriate interfaces, documentation and support.

Used GSM modems are fequently available quite cheaply on ebay.