Ed Morgan acquired the machine (perhaps by finding it, perhaps by obtaining it off somebody else) and then Bernie Harris, a small-time fence in grey-market alien artefacts who filched it out of a biscuit tin found in a lockup owned by Ed Morgan presumably.
Torchwood Three acquired the machine by tracing alien energy signals from the device while still in Harries' possession. After a chase that led her to a train station, Gwen Cooper ended up with Harries' hoodie, with the machine in a pocket. She mentally time-slipped back in time and saw a ghost from World War II, not a phantom in the conventional sense, but a quantum echo of the long-ago emotional state of a living person, Tom Flanagan. The other half of the machine, also at Bernie's, snapped in neatly with the first and picked up visions of the future.
The Transducer used nanotechnology. It converted the quantum traces of emotional events, both past and future, into a form that humans could mentally experience. (TV: Ghost Machine) Jack believed that it worked as a navigational device for travellers across the dimensions who would use quantum traces to orient the flight of their craft. (WEB: torchwood.org.uk)
When activated, apparently by touching the buttons on the front, the user was shown a emotional event from the past or future. As well as showing the actual event, the Transducer also transmitted the thoughts of the people in the event. (TV: Ghost Machine)
- When the events were seen, more negative events were shown darker and and less colourful, whereas positive events were shown brighter and more vibrant. This may suggest the events were colour-coded for the emotional states.