# Can the test room isolator be powered by DC?

When the college entrance examination and high school entrance examination are held as scheduled every year, some schools will be designated as examination rooms. During the construction of standardized examination rooms, these schools will purchase and install a large number of examination room shields. Then, a large number of examination room shields will be used in the power supply. How to solve it?

Most of the test room jammers used in the standardized test room are low-power cell phone jammer. Its RF transmission power is usually 2-3W per frequency band, and the total RF transmission power of the whole machine is about 30W. The overall power consumption of a test room isolator is roughly in the range of 120-200W. The test room shield itself will be equipped with a switching power supply (or a power adapter), which is used to convert the AC 220V into 5V or 12V DC to provide power consumption for the device.

Because there will be dozens or even hundreds of test classrooms in a school, the number of shields in the test room corresponds to it. In order to turn on or off such a large number of test room isolators in a unified and centralized manner, the easiest way is to concentrate the power supply of all test room isolators in each teaching building on one AC power supply line.

However, in many standardized test classrooms, monitoring systems, closed-circuit television systems, and campus broadcasting systems are installed at the same time. These devices are usually equipped with switching power supplies. Therefore, some customers ask whether they can use the test room. The power supply of the shielding device should be powered by the DC on the monitoring line instead? The purpose of this is to save a part of the cost of switching power supply and power circuit layout.

This method is not desirable. The main reason is that the power consumption of each test room isolator is not low. When using AC 220V power supply, the current in the power line is close to 1A, and multiple test room isolators are connected in parallel. When on the power line, the total current value only accumulates slowly. If it is replaced with DC power supply, according to the conversion of power consumption, current and voltage, the current occupied by a single test room shield will reach 10-20A. When multiple test room shields are connected in parallel on a DC power line, the total current will reach several hundred A, which is obviously not in accordance with the correct circuit usage specification.