Abstract: A quantum key distribution (QKD) system is provided that makes use of a quantum signal of polarized photons and comprises a QKD device and complimentary QKD apparatus. The QKD device has a QKD subsystem comprising one of a QKD transmitter and receiver for inter-working with a complimentary QKD receiver or transmitter of said apparatus. The device also has an alignment subsystem arranged to wirelessly interact with the QKD apparatus to enable generation of user feedback and/or adjustment signals for use in aligning the QKD transmitter and receiver such that the QKD transmitter is pointing at the QKD receiver and the polarization axes of the QKD transmitter and receiver are aligned.

Abstract: A coke oven wall (4) comprising a plurality of bricks (38, 42, 46, 120) laid so as to define first and second wall faces (40, 44), and plurality of flue cavities (14) extending therein characterized in that at least part of the wall is made first, second and third bricks (38, 42, 120) which are laid together and define in part the first and second faces and the flue cavities wherein the first brick comprises a first body portion (48) and an inwardly projecting first leg (50), the second brick comprises a second body portion (64) and an inwardly projecting second leg (66) the third brick comprises a flue wall brick (46, 120) which is located between and aligned with the first and second legs.