Call blocking | u verse phone call blocker
You are right about it. Signal jammers may be of two main types: desktop and portable. While desktop models are intended to be used indoors, portable ones are compact enough to be carried with you and used elsewhere. And as they are used outdoors, their work may be influenced by external conditions.
Most signal jammers are working with the same stability in the temperature between 0 and 50 Celsius degrees and between 5 and 80 percent of air humidity. But if they are used, for example, in the desert during the sand storm, their functionality is in danger, especially if they have ventilation slots which can ball up by the sand.
In cases described above you can use jammer for special conditions which is designed for military operations and can resist many different weather types and harsh conditions. It is protected well and can maintain its functionality in wider range of temperatures and humidity level. Special ops need special equipment!
Now you know what conditions are appropriate for signal jammer usage, so when you have more questions, get here again to find the answers :)