Privox push-to-talk: apps, radios and limits

What Privox is

Privox works like a walkie-talkie, but the voice goes over the internet. Hold the button, wait for the "transmitting" sign, speak and let go. One person talks at a time, and everyone in the group sees who is speaking.12

Because the voice goes through a server, distance does not matter. The people in a group can be in one building or in two countries. Every phone or radio needs mobile data or Wi-Fi.1

The Privox home site lists its push-to-talk service as in development.3 Its business page offers a trial at one real site.4

Where Privox runs

You join a group with a personal QR invitation, or with a login and password. Radios use the login.5

The Safari version cannot wake a locked iPhone for an incoming call. Only the TestFlight app can.2

Groups, calls and alerts

Privox says it has these kinds of calls:1

• Group channel: the walkie-talkie part, one speaker at a time.
• Private call: two people talk at once, like a phone call.
• Call group: every phone in the group rings, even when asleep. Whoever answers joins the channel.2
• SOS: reaches the whole organization, across all groups.

Each person shows one of three states: on air, reachable (the phone sleeps but a call wakes it) or offline. The colors update within 60 seconds.12

Groups also have chats with history. Photos and documents can be up to 25 MB, and videos up to 50 MB.1

The dispatcher console

The console runs in a browser, with nothing to install. Privox says it shows the groups, the live channel, the shift with a call button for each person, a map and the chats in one window.14 The map shows each person's callsign and speed. An admin can turn location sharing off for one person.1

A dispatcher can speak into any group without joining it.4 There are four roles: superadmin, admin, dispatcher and user, and each organization is kept apart from the others.12

Sensors in the same channel

Privox can also watch sensors: temperature, humidity, water leaks, doors, motion, power and air quality.1 When a value goes past its limit, the alarm fires once. It goes to the console, to the group's phones and to a manager in Telegram.1

So the people on a shift hear each other and see a warm fridge or an open door in the same app. The demo site has an alarm simulator you can try.6

Where the data is kept

Privox says its server can run in the Privox cloud or on the customer's own server.46 It publishes no hosting region.

The privacy policy says voice passes through the server but is never recorded or stored.7 Messages, files and locations are stored while the account is active.7 Call alerts go through Apple and Google push services. They carry the caller, the callsign and the group name, but no audio or message text.7

The demo site says traffic uses TLS 1.3 and voice uses WebRTC with DTLS-SRTP encryption.6

Price and trial

Privox publishes no price list. Its business page offers a trial at one real site with a real shift. The scope and terms are agreed with each customer.4 The interactive demo is open to anyone. The real app needs an account that an admin creates.67

Limits

• The Android app is not in Google Play, and the iPhone app is only in TestFlight.5
• Bluetooth headsets are not certified yet.2
• The Mini Radio cannot switch groups by itself after a call.2
• Privox publishes no list of tested radios beyond the T320 and the Mini Radio.5
• Privox publishes no gateway to DMR, TETRA or analog radios.

Privox and walkie-talkies

A Privox group and a group of PMR446 or FRS walkie-talkies cannot hear each other. The walkie-talkies talk radio to radio on 446 or 462 MHz. Privox talks through a server over 4G or Wi-Fi.8 A bridge between the two kinds needs a radio gateway, and Privox does not offer one.

Walkie-talkies need no network and no data plan, but they reach a few hundred meters in a town.9 Privox reaches anywhere with signal, but it stops where the signal stops. How the different kinds of radio connect is on the radio types page.

Other push-to-talk services work the same way: Zello Work, TASSTA, WalkieFleet and RealPTT. Some of them sell gateways to ordinary radios. They are side by side on the software page.

Questions

Sources

1. PRIVOX PTT: system overview · Privox
2. PRIVOX PTT documentation · Privox
3. Privox · Privox
4. PRIVOX for security and property operations · Privox
5. PRIVOX PTT downloads · Privox
6. Privox interactive demo · Privox
7. PRIVOX PTT privacy policy · Privox
8. ECC Decision (15)05 on PMR446 · CEPT
9. PMR446 guide · Elektroniskie sakari