The Solution to Power Supply for Exam Room Signal Jammers

Every year, during the scheduled high school and middle school entrance exams, certain schools are designated as exam centers. These schools, during the construction process of standardized exam rooms, purchase and install a large number of exam room signal jammers. However, with the large quantity of signal jammers, how should the power supply be addressed?

## Exam Room Signal Jammers:

The majority of signal jammers used in standardized exam rooms are low-power Cell Phone Jammers. The radio frequency transmission power of each frequency band is typically around 2-3W, with a total radio frequency transmission power of approximately 30W for the entire device. The overall power consumption of a signal jammer is usually within the range of 120-200W. The signal jammer itself is equipped with a switch power supply (or power adapter), which converts the AC 220V into DC 5V or 12V to provide power for the device.

## Power Supply for Multiple Signal Jammers:

Since a school may have dozens or even hundreds of exam rooms, the quantity of signal jammers corresponds to the number of exam rooms. To centrally control the power on/off of these numerous signal jammers, the simplest method is to connect the power supply of all signal jammers in each teaching building to a single AC power line.

## Considerations for Power Supply:

However, in many standardized exam classrooms, surveillance systems, closed-circuit television systems, and campus broadcasting systems are also installed. These devices typically have their own switch power supplies. Some customers have inquired whether the power supply for the signal jammers can be changed to the DC power from the surveillance system, in order to save on the cost of switch power supplies and power line arrangements.

## Infeasibility of Power Supply from Surveillance System:

This approach is not feasible primarily because the power consumption of each signal jammer is not low. When using AC 220V power supply, the current in the power line is close to 1A. When multiple signal jammers are connected in parallel on a single power line, the cumulative current will gradually increase. If the power supply is changed to DC, based on the conversion between power consumption, current, and voltage, the current consumed by a single signal jammer will reach 10-20A. When multiple signal jammers are connected in parallel on a DC power line, the cumulative current will reach several hundred amperes, which clearly does not comply with proper circuit usage standards.

## Conclusion:

In conclusion, the power supply for a large quantity of signal jammers in exam rooms should be centralized and connected to an AC power line. Attempting to use the DC power from surveillance systems is not recommended due to the high current consumption of signal jammers, which would violate proper circuit usage standards. By ensuring a stable and reliable power supply, the signal jammers can effectively fulfill their role in maintaining the integrity of standardized exams.