sentences:  Particular design and engineering challenges were a tamper-resistant PDA retention and ejection mechanism, and a secure loading door latch, to prevent the device spilling ticket stock or batteries if dropped onto concrete from a height of 1.5M.Hyphen Design also developed a cartridge design for holding Z-fold or fan-fold ticket stock.With the horizontally mounted cartridge, a stack of 3 or five or more of the fan-fold stock could easily be drawn into the print head and jam it.