Signal-plans, call-signs and codes were the fundamentals of clandestine communication.

And was the traffic snarl-up no more than a natural hazard of clandestine communication?

In its present form, one-time pad traffic was passed entirely in figures, which would the dangers of clandestine communication.

The network received clandestine communications from Cuba via the Atención numbers station.

The nature of our atmosphere prevents most clandestine communications, and even blocks basic surveillance of us on the ground by remotes.

However, by 1943, Gambier-Parry and his staff had engineered a substantial improvement in clandestine wireless communication.

A courier has no responsibilities other than clandestine communications.

The agent asked for additional biographical information and sought information on how best to conduct clandestine communications.

These were used as retreats in times of attack and for clandestine communication between the religious houses.

It was only in their clandestine written communication that they moved into their own world, what Professor Dyson calls "the underground writing curriculum."