These receivers support computer control. They can be directed by the software to a voice channel. Voice traffic will be heard on the receiver's speaker or headphone jack (not your computer speakers). A receiver so configured operates in a "voice" role. If your receiver also has a discriminator tap, it can operate in a "signal" role. Such receivers are called "Both" receivers. Read this explanation of the different classes and roles of receivers for decoding and voice following.
All models but the PCR-100 include a packet output jack on the back of the radio. This output is discriminator audio. The audio is slightly filtered so 9600 bps EDACS decoding is slightly degraded. A mod exists to bypass this filtering. PCR-100 can be tapped or left as-is for voice only service. For the other receivers, the audio must be "piped" into your computer through a line or microphone jack. Usually a 1/8" mono audio patch cable will suffice. If you wish to use the radio for voice following only, configure it as Control receiver and skip the audio device configuration.
Here are a few mods for the R-2500 - including improved packet output.
Validate your receiver / computer connection with the Icom supplied control software.
The program does not limit you to one or two receivers. You can have as many voice and signal receivers as you like.
You must have one signal receiver to provide control information. To hear voice traffic, you must have one separate voice receiver.
The second VCO is not supported. The program fails to enable the UT-122 P25 voice decoder module when installed. Sorry. If you'd like to see these supported, contact me by gmail or sign up to the Google groups mailing list.