**Explanation:**

Before the advent of semiconductor technology, voltage control applications were primarily achieved using tap changing transformers. Tap changing transformers are devices that allow for the adjustment of the turns ratio of the transformer by changing the position of the tap on the winding.

**Tap Changing Transformers:**

A tap changing transformer consists of a primary winding and a secondary winding with multiple taps. The tap changing mechanism allows for the selection of the desired tap position, which in turn changes the turns ratio of the transformer. This enables the control of the output voltage.

**Advantages of Tap Changing Transformers:**

1. Flexibility: Tap changing transformers offer the flexibility to adjust the output voltage to meet different requirements. This makes them suitable for a wide range of voltage control applications.

2. Reliability: Tap changing transformers have a long history of successful operation and are known for their reliability. They have been widely used in power systems for voltage control and regulation.

3. Cost-effectiveness: Tap changing transformers are relatively cost-effective compared to other voltage control devices, such as cycloconverters or vacuum tubes. They are simpler in design and require less maintenance.

4. Suitable for High Power Applications: Tap changing transformers are capable of handling high power levels, making them suitable for applications where high voltage control is required.

**Limitations of Tap Changing Transformers:**

1. Limited Voltage Range: Tap changing transformers have a limited range of output voltage adjustment. The number of taps on the winding determines the number of discrete voltage levels that can be achieved.

2. Slow Response Time: The response time of tap changing transformers is relatively slow compared to semiconductor-based devices. This limits their application in situations where fast and precise voltage control is required.

In conclusion, tap changing transformers were commonly used for voltage control applications before the development of semiconductor technology. They offer flexibility, reliability, and cost-effectiveness, making them suitable for a wide range of applications. However, their limited voltage range and slower response time compared to semiconductor devices are some of their limitations.