In addition to this, phase 2 radios are backwards compatible with phase 1 modulation and analog FM modulation, per the standard. However, P25 Phase 2 infrastructure can provide a "dynamic transcoder" feature that translates between Phase 1 and Phase 2 as needed. P25 phase 2 products use the more advanced AMBE2+ vocoder, which allows audio to pass through a more compressed bitstream and provides two TDMA voice channels in the same RF bandwidth (12.5 kHz), while phase 1 can provide only one voice channel. Starting around 2012, products became available with the newer phase 2 modulation protocol, the older protocol known as P25 became P25 phase 1. P25 radios are commonly implemented by dispatch organizations, such as police, fire, ambulance and emergency rescue service, using vehicle-mounted radios combined with repeaters and handheld walkie-talkie use. P25 radios are a direct replacement for analog UHF (typically FM) radios, but add the ability to transfer data as well as voice, allowing for more natural implementations of encryption and text messaging. P25 was developed by public safety professionals in North America and has gained acceptance for public safety, security, public service, and commercial applications worldwide. Project 25 ( P25 or APCO-25) is a suite of standards for interoperable digital two-way radio products. JSTOR ( November 2019) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources. For more information and downloads of DSD and MBELIB, visit the RadioReference Digital Speech Decoder page.This article needs additional citations for verification. It is highly recommended that all RF hackers, whether using an SDR or conventional receiver, become acquainted with these programs and examine the Linux program source code. DSD relies on the libraries contained in the required MBELIB package. Additionally, various protocol decodes (P25 among them) provide a running display of certain packet data in the terminal window. DSD is then run (using the appropriate arguments, depending on the mode and parameters involved) with the resulting demodulated speech directed to the soundcard output jack. The program accepts audio taken from the discriminator output from a scanner or amateur radio receiver fed to the soundcard input. DSD is an open source command line program originally coded in C by anonymous for Linux for the purpose of decoding digital protocols via a PC soundcard. Here proct0r links the output from SDR# to a program known as DSD. This is another illustration of the amazing utility of the RTL-SDR and SDR# software.
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