Both of these devices are installed in EFI cars
Emulator: It emulates i.e. gives false impression to the ECU as if the engine is running on petrol. There are a number of emulators and the most common one that emulates false fuel injection to the ECU.
Advancer: It is a device that advances the spark timings while on CNG. It is intended to keep the car well tuned on petrol with ideal timing. If advancer is installed then the spark timing for CNG is not adjusted through distributor.
You can install these by any renowned CNG installer at about Rs.2500/= each (i.e. about Rs.5000/= for both).