what position I should insert the micro sim card: the cut angle should go forward or should it be left behind?
Hello,
Excuse me, I'm pretty newbie.
I have purchased a SIM800 module to send messages with Arduino. I'm not sure in what position I should insert the micro sim card: I already know that the face of the contacts should match, but the cut angle should go forward or should it be left behind?

A more general question: is the position of the micro sim always the same or does it change according to devices? How do you know?

 

There's normally 8 different orientations that a SIM can be inserted into a socket - four with the SIM connectors facing upwards, and four with the SIM connecting downwards.

Then, there's each of the 90 degrees of rotation.

Most SIM sockets will prevent accidental insertion of the SIM that can cause damage - and the best way to do that is to have the triangular cut-out part being inserted first. A triangular section inside the socket will prevent the SIM from being inserted fully when the wrong way around.

Judging from that picture (which I can't seem to zoom in), I would say that the notch needs to be towards the bottom of the picture - i.e. where the extra bit of metal is on the socket (near the silk-screen text). The SIM's contacts needs to be facing the PCB.

The orientation is NOT guaranteed between different SIM socket manufacturers or even models by the same manufacturer.