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 and other kinds of electrical interference will make conversations hard or impossible to understand.

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

Delay the transmission and delivery of telegrams to enemy destinations.

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

Cut telephone and telegraph transmission lines. Damage insulation on power lines to cause interference.

(d) Mail

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

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.

Audiences can ruin enemy propaganda films by applauding to drown the words of the speaker, by coughing loudly, and by talking.

Anyone can break up a showing of an