There is provided a chain guide capable of preventing a reduction in the durability of the chain guide. The inputoutput buffer includes a reference power generation circuit connected to a high voltage power supply and a low voltage power supply to convert the voltage of an external voltage signal and generate reference power. The interior portion is connected to the bypass section, and the product that flows through the bypass section is supplied to the interior section of the transparent member. The generated signature of the message is compared to a stored signature. In addition, the customer descriptor may also include Quality of Service information, allowing the recipient Provider Edge Router or ATM switch to afford the appropriate QoS level accordingly.