(1) At office, hotel and exchange switch boards delay putting enemy calls through, give them wrong numbers, cut them off “accidentally,” or forget to disconnect them so that the line cannot be used again. (2) Hamper official and especially military business by making at least one telephone call a day to an enemy headquarters; when you get them, tell them you have the wrong number. Call military or police offices and make anonymous false reports of fires, air raids, bombs. (3) In offices and buildings used by the enemy, unscrew the earphone of telephone receivers and remove the diaphragm. Electricians and telephone repair men can make poor connections and damage insulation so that cross talk and other kinds of electrical interference will make conversations hard or impossible to understand. (4) Put the batteries under automatic switchboards out of commission by dropping nails, metal filings, or coins into the cells. If you can treat half the batteries in this way, the switchboard will stop working. A whole telephone system can be disrupted if you can put 10 percent of the cells in half the batteries of the central battery room out of order. (b) Telegraph (1) Delay the transmission and delivery of telegrams to enemy destinations. (2) Garble telegrams to enemy destinations so that another telegram will have to be sent or a long distance call will have to be made. Sometimes it will be possible to do this by changing a single letter in a word—for example, changing “minimum” to “miximum,” so that the person receiving the telegram will not know whether “minimum” or “maximum” is meant. (c) Transportation Lines (1) Cut telephone and telegraph transmission lines. Damage insulation on power lines to cause interference. (d) Mail (1) Post office employees can see to it that enemy mail is always delayed by one day or more, that it is put in wrong sacks, and so on. (e) Motion Pictures (1) Projector operators can ruin newsreels and other enemy propaganda films by bad focusing, speeding up or slowing down the film and by causing frequent breakage in the film. (2) Audiences can ruin enemy propaganda films by applauding to drown the words of the speaker, by coughing loudly, and by talking. (3) Anyone can break up a showing of an enemy propaganda film by putting two or three dozen large moths in a paper bag. Take the bag to the movies with you, put it on the floor in an empty section of the theater as you go in and leave it open. The moths will fly out and climb into the projector beam, so that the film will be obscured by fluttering shadows. (f) Radio (1) Station engineers will find it quite easy to overmodulate transmissions of talks by persons giving enemy propaganda or instructions, so that they will sound as if they were talking through a heavy cotton blanket with a mouth full of marbles.