SECRET military reservations. In this connection, however, there was probably less risk in the case of circuits inside such reservations than in the case of those outside, since engineers working on circuits within a military reservation were more likely to be under supervision. The Air Ministry, nevertheless, regarded it as important that the risks within military reservations should be carefully considered. (f) The chief danger appeared to lie in the fact that the frames and repeater stations in the teleprinter circuits throughout the country were visited periodically by engineers for the purpose of testing and maintaining the circuits.