interface RS-232 GSM module

Hello Friends
I’ve bought this Siemens TC-35i GSM module:

However I don’t know how to wire it to the Arduino, I didn’t find anything on the Playground except software related things.

Does it need any chip (usually from Maxim) for voltage translation? I read Arduino 2009 has UART TTL 5Volts serial connection on Pin 0 and 1.
Any protection diodes for ESD?

Does it need any chip (usually from Maxim) for voltage translation?

I would guess yes; the DB9 connector usually indicates true RS232 signals, and I think I can make out a Sipex IC near the DB9. Sipex manufactures MAX232 family clones, among other things.

Any protection diodes for ESD?

Nope, the RS232 level translator (e.g. MAX232) usually has ESD protection as well.

-j

Thank you kg4wsv for the reply! Yes you guessed it, it's a Sipex SP3239ECA 3.0 to 5.5V RS-232 transceiver. As Arduino have already 5V signals, can I wire it directly to the GSM module? How can I wire it? I don't understand why the used a 3 to 5.5V chip when computer's RS-232 signal voltage is +12/-12V For convenience this is the DB9 RS-232 pinout

I don't understand why the used a 3 to 5.5V chip when computer's RS-232 signal voltage is +12/-12V

That "3V to 5.5V" is on the logic side of the chip - it can operate on 3.3V, unlike the MAX232 which needs 5V. The RS232 side is in fact +12V/-12V.

You still need an RS232 transceiver for the Arduino.

Connect TX to RX, RX to TX, and GND to GND.

-j

Great, so I just need a MAX232 and power it through the Arduino +5V, am I right? I read MAX233 is the same but without external caps. Where is the downside? I suspect it's about the cost, as the 233 costs twice the 232...

Thank you for the patience, I'm a bit more on the software side - in fact I already learned all the necessary AT commands through a GSM USB modem..

Where is the downside? I suspect it’s about the cost, as the 233 costs twice the 232…

That’s it. The 233 is a bit bigger, too, although probably not as big as a 232+5 TH caps.

-j

Thank you for the reply!

I read there are several MAX232 clones, like ones from ST and TI that can cost 10x less. Can I go away with them or better to stick to the original one?

Clones are just fine. I've used TIs, and several devices I own have the Sipex.

-j