Some cell phone jammers look like real cell phones. Others are the size of a briefcase or larger.
Larger jammers used by police and military can be installed in the convoy to protect the safety of the convoy.
From an electronic point of view, cell phone jammers are very basic devices. The jamming device overloads the mobile phone by sending signals at the same frequency and high enough power, so that the two signals collide and cancel each other out. Cell phones are designed to increase the power when they encounter low level interference, so the cell phone jammer should recognize and match the increase in power of the phone. The simplest jammer only has an on / off switch and an indicator light to indicate that it is on. More complex devices have switches that can activate different interference frequencies. The jammer components include:
antenna
Each jamming device has an antenna to send a signal. Some are contained in the electrical cabinet. On more powerful devices, the antenna is external to provide greater range and can be adjusted for a single frequency.
Circuit
The main electronic components of the jammer include:
Voltage Controlled Oscillator - Generates radio signals that will interfere with cell phone signals
Tuning circuit - sending a specific voltage to the oscillator to control the frequency at which the jammer broadcasts its signal
Noise generator - generates random electronic output in specified frequency range to interfere with mobile phone network signal (part of tuning circuit)
RF Amplification (Gain Stage) - increases the RF output power to a level high enough to block the signal.
Power source
Small disruptive devices are powered by batteries. Some look like cell phones and use cell phone batteries. A more rugged device can be plugged into a standard outlet, or it can be connected to the vehicle's electrical system.
Check your phone - if your phone battery is okay and you want to continue the call, try leaving the area. You can get rid of the jammer in just a few steps.