You can download TFR via the Steam Workshop or over at
http://radio.task-force.ru/en/
The mod folder also includes the Teamspeak AddOn that needs to be installed. For those who have no clue how this mod now actually works, here's a quick guide.
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We all have to be in the same TS channel. Once you connect to the server, the TS Plugin activates itself. From now on you're not able to talk ingame anymore without either being in close proximity to someone or use the radio. You're also not able to talk to each other 'just like this' in TS anymore, as long as you're on the server.
By default, everyone should have the AN/PRC-152 radio equipped (if not, get it). That is a short wave (SW) radio that has a range of up to 5km. Every vehicle in the game also has a long range (LR) radio that goes up to 20km. There are also mobile LR radios that are backpacks. Every radio has a variety of channels with different frequencies. Same frequency = you can talk to each other (duh).
CTRL + P brings up the SW radio. You can manually change frequencies there. Keep in mind to click the Enter button on the radio to confirm the change.
ALT + P does the same for the LR radio.
CAPS LOCK lets you talk over SW.
CTRL + CAPS LOCK lets you talk over LR.
If you're close to each other, proximity voice chat will kick in. If you've ever played GTA5 RP, you should know how that works.
If you want another overview over all the keys, open your map ingame, go to Radio in the top left, click controls and there you have it.
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Elektro also installed the following mods for a bigger arsenal of weapons and vehicles:
RHSUSAF,
RHSAFRF.