Conditionally stable system:
A conditionally stable system is a type of system that exhibits stability within a certain range of conditions but becomes unstable outside that range. In other words, the stability of the system depends on specific conditions.

Poor stability at reduced values of open-loop gain:
When the open-loop gain of a system is reduced, it means that the system is less able to amplify the input signal. In a conditionally stable system, this reduction in open-loop gain can lead to poor stability.

When the open-loop gain is reduced, the system's ability to counteract disturbances and maintain stability is compromised. The feedback loop in a control system relies on the open-loop gain to provide sufficient amplification to overcome disturbances and maintain stability. If the open-loop gain is reduced, the system may not be able to compensate for disturbances effectively, leading to instability.

Explanation:
To understand why a conditionally stable system exhibits poor stability at reduced values of open-loop gain, consider the following points:

1. Feedback loop: In a control system, the open-loop gain represents the amplification of the input signal before it is fed back into the system. The feedback loop uses this amplified signal to generate the control signal that drives the system towards the desired output.

2. Counteracting disturbances: The open-loop gain plays a crucial role in counteracting disturbances. Disturbances can be external factors that affect the system's behavior, such as noise or changes in the input signal. The open-loop gain amplifies the effect of these disturbances, allowing the system to respond effectively and maintain stability.

3. Reduced open-loop gain: When the open-loop gain is reduced, the system's ability to amplify the input signal is diminished. As a result, disturbances may have a greater impact on the system's behavior. The reduced amplification can result in the system being unable to counteract disturbances effectively, leading to instability.

4. Poor stability: Poor stability refers to the system's inability to maintain its desired behavior in the presence of disturbances. In a conditionally stable system, the stability is dependent on certain conditions. When the open-loop gain is reduced, these conditions are not met, and the system may become unstable.

Conclusion:
In summary, a conditionally stable system exhibits poor stability at reduced values of open-loop gain. The reduced open-loop gain diminishes the system's ability to counteract disturbances effectively, leading to instability. Therefore, it is important to ensure that the open-loop gain is maintained within the appropriate range to achieve stability in a conditionally stable system.