A recorder inside a travelling package should ideally measure internal and external relative humidity, internal and external temperature, internal pressure and maximum shock in three directions. Investigations have concentrated on clockwork recorders with DC circuitry to avoid the possibility of interference with flight equipment in the aircraft. The most difficulty has been encountered with a sensor for relative humidity. A complete apparatus will weight 5 kg, and measure 23 x 14 x 10 cm; without pressure recording this can be reduced to 2.75 kg and 18 x 18 x 10 cm.