Summary: The Soundcast ACR 212 is a recever unit. It works in conjunction with the Soundcase Transmitter (sold separately). The Soundcast system is relatively new, and includes a variety of transmitters and receivers and speakers (indoor and outdoor). It is not cheap. But it works.
The Soundcast system allows you to connect an Ipod, Mp3 player, home audio system, computer, etc. to a transmitter about the size of a paperback. The transmitter allows headphone and line level connections. Each transmitter can handle 2 receivers, though you can piggyback transmitters to each other to allow a total of 4 receivers receiving the same audio signal, or 2 separate zones with each transmitter controlling 2 receivers, and each receiving separate audio sources (ie. music for a pool party outside, and more relaxing music inside).
The receiver is the same size as the transmitter. It comes with line out connections for you to connect to an amplified source (either an amplifier or a powered speaker).
The range is 150' through walls, 350' outdoors. I confirmed this.
It broadcasts in the 2.4mhz range, but uses freq skipping technology to avoid interference from microwaves, phones and wireless computer networks. I did not notice ANY interference. Impressive. I did not notice any impact on my wireless network throughput either.
You can also get an Ipod specific sender/receiver for more money. Controls for changing the ipod source material are found on the receiver unit. Check out their wbsite for more details.
I use it with my media PC to send music throughout the house to some some amplified spks outside, as well as some areas in the house.
You can also buy speakers from Soundcast that have the receiver unit built in (and controls for an Ipod -- though they do sell versions without the ipod controls for a lower cost).
Case is tough, and there are no antennas visible. Other than the cables from the receiver to the amp, there is a 6v power cord.
No on/off switch! Well, that is a drawback sorta, I have it plugged into a switched outlet on my amps, so if the amps are off, so is the receiver. My guess is later models will have the switch to be more "green".
Overall, extremely pleased. I have used other wireless systems with mixed results. Whether it is wireless over the air, or wireless via homeplug, I have had problems with interference.
And I have no desire to hardwire speakers at this time. This really fit the bill. This is a very good system. Pricey, but very good.