Data Interface

The audio jack is one of the interfaces on mobile devices and tablets, it's mostly used to play music ,but it can also be used to receive and decode data. It can not be connected directly to a receiver, this can damage the receiver/scanner. A simple circuit is needed to connect a receiver to this audio jack. ( phone/tablet mic-in). If POCSAG is decoded most often the unfiltered audio from the receiver is used (discriminator-output). Some scanners have a discriminator output build in ,but most don't. So if you don't want to crack open your brand new receiver and do some soldering you can try the amplitude decoding mode which uses the earphone output from your receiver or scanner. The receivers amplifier has an analogue filter at its output causing distortion,it seems that the signal collapses or rises after one bit high or one bit low,this is why it's so hard to decode with the earphone signal, also each type receiver has different filters and amplifier so a standard setting is almost impossible Another problem is the different specs of the MIC-in circuit from the different manufacturers of android devices which results in different amplitude levels when using the same receiver but different devices. So after all this how can the right audio level be found. Well it's been tried with this app with the interface circuit. This app is a test version there are still some errors in it, it is used to test if the circuit works on the different devices but it can decode the POCSAG protocol Function 3 alpha-numeric most of the time ,however it will not work on some devices.