By looking at the video, we in the business can tell a great deal.
The toner cartridge was installed.
The cell phone and other electronics as well as wiring, are contained within the HP LaserPrinter.
The powerful and hard-to-detect type of explosive known as PETN, the same substance used by AQAP in a failed plot to blow up a U.S.-bound passenger plane last Christmas Day, looks to be packed into the toner cartridge. (White substance)
So basically, the explosive material was packed into the toner cartridge and wired into the timer, power source, and other detention electronics, bolted on somewhere in the printer.
From the outside, the unit looks as tame as ever. As to how these bombs were detected, officials said the plot was discovered thanks to intelligence passed from Saudi Arabia. Without that tip, it's unclear whether anyone would have discovered the bombs before they were airborne — or on U.S. soil. Great, no high-tech solution here, just more heavy TSA petting before boarding.
There is absolutely no doubt that HP had nothing to do with this, and is indeed a big victim here.
DOTC, August 18, 2009, SEC Asked HP About Middle Eastern Dealings - Back in February
DOTC, January 9, 2009, HP To Stop Selling in Iran - Power of The Press
DOTC, December 29, 2008, HP Printers Sold in Iran - The Unholly Alliance -
Printer Bomb Plot from Matthew Cole on Vimeo.