Abstract: A waterproof connector comprises a terminal, a housing and a seal member. The housing is provided with an attachment portion. When the attachment portion is viewed along a front-rear direction, the attachment portion has an outer circumferential shape including first sides and first coupling portions. The seal member is formed of elastic material and is attached to the attachment portion. When the seal member is viewed along the front-rear direction, the seal member has a closed-ring shape including second sides and second coupling portions. The second sides correspond to the first sides, respectively. The second sides include at least one specific second side. L1 > L2, where L2 is a length of each of the second sides in a state before the seal member is attached to the attachment portion, and L1 is a length of the corresponding first side.

Abstract: There is provided a controller that prevents any external power source from supplying its power if a host device and a monitoring device are not connected exactly through optical extension cables based on DVI standard, and that prevents a sequence for digital transmission of a video signal from being started if the external power source remains off. Only when the proper (DDC+5V) signal is generated from the host device and the external power source has been turned on, the (DDC+5V) signal is transmitted to the monitoring device, and when it is detected in the monitoring device that the transmitted signal is the proper (DDC+5V) signal, the (DDC+5V) signal is transmitted to the monitoring device.

Abstract: There is provided a controller that prevents any external power source from supplying its power if a host device and a monitoring device are not connected exactly through optical extension cables based on DVI standard, and that prevents a sequence for digital transmission of a video signal from being started if the external power source remains off. Only when the proper (DDC+5V) signal is generated from the host device and the external power source has been turned on, the (DDC+5V) signal is transmitted to the monitoring device, and when it is detected in the monitoring device that the transmitted signal is the proper (DDC+5V) signal, the (DDC+5V) signal is transmitted to the monitoring device.

Abstract: A communications system has two transmission circuits, each transmitting a multiplexed signal in both ways. A repeating installation used therein selects either one of the two transmission circuits and terminates management information contained in a signal which flows through a transmission circuit selected by the selecting unit. The repeating installation sets the other non-selected transmission circuit to be in a high impedance state. The selection and termination are commonly performed for the two transmission circuits, and the repeating installation further extracts the management information transmitted and outputs the management information to be outputted. The management information includes a section overhead having management information concerning a repeating section of the communications system, and the repeating installation does not terminate management information concerning a multiplex section. One of the two transmission circuits includes a spare transmission circuit.