Is it possible to change my Philips DSX 6170/68A DVB to a free to air or other CI i.e Viacess? Presently my receiver has a cyprtoworks system. I want to know if it can be change to Free to Air or other CI.
All receivers can receive FTA transmissions. They are simply the unencrypted signals.
Some receivers can additionally receive encrypted transmissions, and decrypt them using various kinds of Conditional Access Modules (CAMs)
Receivers which have only "embedded" CAMs are the least flexible. These include the Sky digiboxes, which have embedded Videouard CAMs. They will not accept any other kind of decryption module, and the embedded CAM can not be re-coded in any way (it is hardware-constrained).
But some receivers have slots for the so-called Common Interface CAMs (CI CAMs). A CI-CAM is interchangeable. If your receiver is a CI-type and has a removable Cryptoworks CAM then you can simply replace that CAM with a different kind of CI CAM (eg Seca, Irdeto, Nagravision, Viaccess,...). That's why they call it a Common Interface CAM.