The Government recently changed the NSW communications network used by a multitude of emergency and non-emergency agencies. This includes private companies such as electric companies, shopping centres, and any other companies with the need to communicate over long distances via two-way radio. It uses technology called P25 (Project 25) but is also referred to as APCO25 and is now the national standard in New South Wales and some other states.

Those systems are referred to as Trunked Systems—remember that term. Trunking is an essential part of the PSN or previously GRN. Frequently Asked Questions about the Public Safety Network's technical aspects and terminology. When buying a scanner, read the following carefully and check the page "Scanner Purchase Guide".

When in operation and used by agencies, talkgroups allow the logical grouping of radio users to ensure they can communicate with each other. Inside a talkgroup, sharing takes place to allow all radio users of a specific talkgroup to speak to one another and to the operator, if applicable. If a user in, for example, the SES broadcasts a message in one of their assigned talkgroups, all other users on that talkgroup are able to hear that message.

Think of it like a WhatsApp group. In a scanning context, this is important as we must know who the talkgroups belong to, label each talkgroup, and categorize it to understand who is being listened to.

The latest upgrades have seen the PSN move to the Phase II system. The full technical description is APCO25 Phase I or II. While some systems still use Phase I, a majority of broadcast towers have now been upgraded (or enabled) for Phase II. Some temporarily run on both systems at the same time. However, in order for a hobbyist to continue to listen to the PSN and its users, a Phase II capable scanner is an absolute requirement.

If you are in the market of buying a scanner, ensure it is capable of receiving APCO25 digital AND Phase II. Otherwise, all you'd be able to listen to is aviation, the occasional user still on Phase I, and CB radio communications. That said, some Public Safety Network sites are still backwards compatible, but this is becoming rare these days.

While Phase I provided flexibility and a lot of talkgroups for a great number of users, the PSN would run out of space, so to speak. To keep things simple, Phase II is a natural evolution of the P25 network. It allows users to use a more advanced vocoder—AMBE2+—allowing audio to pass through a more compressed bit stream. Additionally, to allow for more capacity, Phase II allows two voice channels to pass through within a 12.5 kHz radio frequency bandwidth.

Phase II is also backwards compatible, allowing the system to be rolled back should the need arise.

The NSW Police Force went ENC (Encrypted) in the mid-2010s. This stops unwanted listeners from monitoring those talkgroups; the unintended side effect is that the lack of oversight may breed corruption, coverups, and secrecy.

Everyone agrees that some channels are not meant for public ears, such as special operations groups, drug enforcement, etc. However, for most others, it is merely a nuisance. Encryption works by using cryptographic algorithms, a topic which is complex, but in simple terms, there are several different types of encryption methods such as end-to-end, asymmetric encryption, and symmetric encryption. Other ESOs are likely to follow over the next few years, with Ambulance NSW being the next in line to adopt encryption of the same type as what NSW Police, Department of Corrections, and the NSW Sheriff's Office use.

Keys to decode the encrypted voice channels are cycled usually on a weekly basis and are nearly impossible to break. More importantly, it is also illegal to circumvent or break said encryption, and if someone were successful (for example, with a stolen radio), they would get caught within hours as the location would be able to be triangulated and locked out of the network remotely. I am not a lawyer, but expect jail time. Please don't email me or ask on Discord on how to break the encryption for obvious reasons.

On the NSW Public Safety Network, control channels serve as the central traffic manager for every radio site across the state. Instead of carrying voice conversations, a dedicated frequency at each tower continuously broadcasts digital data to communicate with all radios within range.

When a responder presses the Push-To-Talk button, their radio sends a rapid request over the control channel containing their unit ID and talkgroup. The network's master controller processes this request, assigns an available voice channel, and instantly commands all radios in that talkgroup to switch to that frequency to convey the call. Once the conversation ends, the radios automatically return to monitoring the control channel for the next command.

Control channels are vital to emergency communications because they maximize spectrum efficiency, allowing dozens of frontline agencies like Fire & Rescue, RFS, SES, and NSW Ambulance to dynamically share a limited pool of frequencies. This centralized coordination manages emergency priority, ensuring critical transmissions and duress alarms jump to the front of the queue during major disasters.

Furthermore, the control channel handles automated background tasks such as radio registration, cell tower handoffs as responders travel, and unit tracking, while allowing scanners and network monitoring systems to seamlessly follow active voice calls across the state.

A Radio ID (RID)—also known as a Unit ID (UID)—is a unique numerical address assigned to every individual physical handset, vehicle radio, and dispatch console operating on the NSW Public Safety Network (PSN). While a Talkgroup ID acts like a shared channel that multiple users listen to, the RID acts like a radio's personal phone number or MAC address.

On the digital P25 Phase 2 network, RIDs are typically seven-digit numbers allocated in designated blocks to specific emergency service agencies (such as Fire & Rescue NSW, the SES, or NSW Police). For example, a SES NSW unit use ID range 204#### - 206####, while NSW Police radios use the 021#### - 219#### range. Every time a user presses the Push-To-Talk button, their radio automatically transmits its RID over the network alongside the voice packet.

RIDs are vital for accountability, safety, and operational control across the state's mission-critical network. They allow dispatchers to instantly identify who is speaking on a busy channel and automatically map unit locations or status updates. Crucially, when a responder activates a duress alarm, the system uses the RID to immediately highlight which specific radio and vehicle triggered the emergency, even if the user cannot speak.

Network administrators also rely on RIDs for security and traffic management, using them to authenticate authorized radios, deny network access to lost or stolen units, grant dynamic call priorities, and enable selective private calling between individual units.