Larger equipment will require an array of sound attenuators, otherwise known as an attenuator bank. Q-switching is achieved by putting some type of variable attenuator inside the laser's optical resonator. The two resistors R and R act only as a "pure" attenuator (voltage divider). An attenuator (resistive divider) can be used to minimize loading. In contrast, an electrically controlled attenuator can provide adaptive power optimization. A typical attenuator circuit is the L pad. Fiber ports designed for long-haul wavelengths require a signal attenuator if used within a building. The attenuator two-port is generally bidirectional. It is also possible to implement a flat frequency response attenuator. The power entering the slotted line is controlled by a rotary variable attenuator (4). Here, the Q-switch is an externally controlled variable attenuator. A precision variable attenuator is often incorporated in the test setup to improve accuracy. The topologies shown in figure 1.7 are commonly used for filter and attenuator designs. Four fundamental attenuator circuit diagrams are given in the figures on the left. To achieve meaningful noise reducion in a relatively short length, a sound attenuator is used.