"1953." Harry read through the record. "Similar to the signal characteristics we sensed today. More than seventy years, and the signal hasn't changed much."
"Just like Grímsey Island," Cassandra said. "A stable intermediate node."
The next morning, they returned to the north side of the island. Harry made a more careful sensory check near the rock face, letting the signal spread from his palm up his wrist as he distinguished the fine structure of its continuous vibration.
The main vibration frequency and period were stable. Within the nested sequence of high-frequency pulses, one pattern appeared repeatedly: pulses of varying lengths at fixed intervals, with an encoding style similar to Grímsey Island's, but slightly different.
"The encoding is clearest here." He stood up and spoke to Isabelle. "It matches Grímsey Island's, but there are slight differences.
"There's some kind of correspondence between the encoding at the two nodes, like different versions of the same system."
Isabelle recorded his findings and compared them remotely with the Technical Group's database.
The Technical Group's reply arrived that afternoon: Jan Mayen Island's encoding was related to Grímsey Island's, and was a variant of it.
The Technical Group believed that Jan Mayen Island was a receiving node extending northeast from Grímsey Island, responsible for relaying signals from Grímsey Island to the network on mainland Norway.
"Jan Mayen Island is an intermediate station between Grímsey Island and mainland Norway." Harry read through the Technical Group's reply. "The signal from the North Pole reaches Grímsey Island first. Then one line branches off from Grímsey Island to Jan Mayen Island, which passes it on to mainland Norway."
"That gives us a more complete chain for the whole network," Cassandra said. "From the North Pole to Grímsey Island, then three lines branch off from Grímsey Island: one to southern Iceland,