WesTech GAC contactors can be supplied in an open-top gravity system or, more commonly, in pressure vessels. They are typically designed with a conical underdrain for convenient GAC replacement.
By contrast, the HomePod is essentially an extension of the iPhone, like an accessory. When someone asks the HomePod to open a third-party app, the request wonât go directly to the cloud, as with the Echo, but to an iPhone. As a result, developers can't write apps for the HomePod. They must create tweaked versions of existing iPhone apps.
Apple hasn't announced an exact date for the release of the HomePod. All we know right now is that it'll be available sometime in December 2017. In the past, Apple has begun accepting pre-orders on its website for new devices like the iPhone 7 one week before they arrive in stores.