New Delhi, Oct. 13 -- where does the heat go? According to two Apple engineers, part of the answer runs through the hinge. The iPhone Duo uses a flexible graphite pipe to carry heat between the phone's two halves, PCMag reported on October 12 after interviewing Dan Murray, Apple's vice president of silicon engineering, and Banafsheh Barabadi, its senior manager of thermal product design.

The design targets a problem that conventional phones do not have. A slab-shaped handset can spread heat across a single back panel. A book-style foldable divides its parts between two halves joined by a hinge, which is a moving joint and not an obvious route for heat. PCMag's interview centres on how Apple keeps its A20 Pro processor from overheating in...