>Knowing which boat was where allows them to determine who might be meeting the smugglers. A signal lamp/ aldis lamp/ Morse lamp during World War I, German sig

>Knowing which boat was where allows them to determine who might be meeting the smugglers. A signal lamp/ aldis lamp/ Morse lamp during World War I, German signalers used optical Morse transmitters called Blinkgerät, with a range of up to 8 km (5 miles) at night, using red filters for undetected communications. They continue to be used to the present day on naval vessels and for aviation light signals in air traffic control towers. This then brings the states mainland communication monitoring into play, because even though some part, some nod of the communication takes place in secret like two people having a conversation passing in the street, subsequent communication channels can be observed over time, which can then expose the use of signal lamps as the form of communication. I think most people dont realise how easy it is to extract information from people without them knowing.