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An RF converter circuit 11 that constitutes a video signal superposing/power deriving unit 100 converts video signals generated from images taken by a surveillance camera 10, which derives a direct current voltage as a driving power from an antenna lead-in wire 6 through a filter circuit (LPF circui

An RF converter circuit 11 that constitutes a video signal superposing/power deriving unit 100 converts video signals generated from images taken by a surveillance camera 10, which derives a direct current voltage as a driving power from an antenna lead-in wire 6 through a filter circuit (LPF circuit 12), to radio-frequency signals. The radio-frequency signals are transmitted through the antenna lead-in wire 6 to a television receiver 2. Images taken by the surveillance camera 1 can be viewed on the television receiver 2 only by selecting the channel assigned to the surveillance camera 1. Accordingly, the driving power for the surveillance camera 1 is not relied upon a solar battery or secondary batteries, and wiring work therefor may be simplified.

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1. A transmitter for a surveillance camera system, which transmits images taken by a surveillance camera to a television receiver, comprising:a power deriving circuit that derives driving power for the surveillance camera from an antenna lead-in wire; and a radio-frequency converter circuit that con

1. A transmitter for a surveillance camera system, which transmits images taken by a surveillance camera to a television receiver, comprising:a power deriving circuit that derives driving power for the surveillance camera from an antenna lead-in wire; and a radio-frequency converter circuit that converts video signals generated from the images by the surveillance camera into radio-frequency signals, wherein the radio-frequency signals corresponding to the images taken by the surveillance camera are transmitted through the antenna lead-in wire to the television receiver. 2. A transmitter for a surveillance camera system according to claim 1, further comprising a video signal superposing/power deriving unit that includes the radio-frequency converter circuit and the power deriving circuit, wherein the video signal superposing/power deriving unit is provided separately from the surveillance camera; andwherein the video signal superposing/power deriving unit is connected with the surveillance camera and the antenna lead-in wire. 3. A transmitter for a surveillance camera system according to claim 1, further comprising a video signal superposing/power deriving unit that includes the radio-frequency converter circuit and the power deriving circuit, wherein the video signal superposing/power deriving unit is provided in the surveillance camera.4. A transmitter for a surveillance camera system, which transmits images taken by a plurality of surveillance cameras to one or more of television receivers, comprising:a plurality of power deriving circuits that each derive driving power for corresponding one of the surveillance cameras from an antenna lead-in wire; and a plurality of radio-frequency converter circuits that each convert video signals generated from the images by corresponding one of the surveillance cameras into radio-frequency signals, wherein the radio-frequency signals corresponding to the images taken by each of the surveillance cameras are transmitted through the antenna lead-in wire to the television receivers; wherein radio-frequency signals from each surveillance camera are different in frequency band from those from every other surveillance camera, so that a different channel of the television receivers is assigned to the radio-frequency signals from each surveillance camera. 5. A transmitter for a surveillance camera system according to claim 4, further comprising a plurality of video signal superposing/power deriving units that each include the radio-frequency converter circuit and power deriving circuit each corresponding to one of the surveillance cameras, wherein the video signal superposing/power deriving units are provided separately from the surveillance cameras; andwherein the video signal superposing/power deriving units are connected with the corresponding surveillance cameras and the antenna lead-in wire. 6. A transmitter for a surveillance camera system according to claim 4, further comprising a plurality of video signal superposing/power deriving units that each include the radio-frequency converter circuit and power deriving circuit each corresponding to one of the surveillance cameras, wherein each video signal superposing/power deriving unit is provided in the corresponding surveillance camera.7. A transmitter for a surveillance camera system according to claim 1, further comprising:a detection unit that detects a significant change in a location under surveillance; and a notification unit that notifies a television viewer of detection of the significant change when the detection takes place. 8. A transmitter for a surveillance camera system according to claim 4, further comprising:a plurality of detection units that each detect a significant change in a location under surveillance; and a plurality of notification units that each notify a television viewer of detection of the significant change when the detection takes place. 9. A video signal superposing/power deriving unit comprising:a power deriving circuit that derives driving power for a surveillance camera from an antenna lead-in wire; and a radio-frequency converter circuit that converts video signals generated by the surveillance camera into radio-frequency signals, wherein the radio-frequency signals corresponding to the images taken by the surveillance camera are transmitted through the antenna lead-in wire to the television receiver. 10. A transmitter for a surveillance camera system according to claim 1 further comprising a power supply control circuit that permits power supply to the surveillance camera and transmission of radio-frequency signals to the television receiver when a significant change in a location under surveillance is detected.11. A surveillance system comprising:a surveillance camera that uses as driving power a direct current voltage derived by a filter circuit from an antenna lead-in wire to take images to be transmitted to a television receiver; a radio-frequency converter circuit that converts video signals generated from the images by the surveillance camera into radio-frequency signals, wherein the radio-frequency signals corresponding to the images taken by the surveillance camera are transmitted through the antenna lead-in wire to the television receiver; and a power supply control circuit that permits power supply to the surveillance camera and transmission of radio-frequency signals to the television receiver when a significant change in a location under surveillance is detected. 12. A surveillance system according to claim 11, wherein the power supply control circuit includes:a sensor circuit that detects a significant change in a location under surveillance; a filter circuit that derives the direct current voltage from a channel superposed in the antenna lead-in wire and supplies same to the sensor circuit; and a switching circuit that starts the power supply to the surveillance camera and the transmission of radio-frequency signals to the television receiver when the sensor circuit detects a significant change in a location under surveillance. 13. A surveillance system comprising:a plurality of surveillance cameras that each use as driving power a direct current voltage derived by a filter circuit from an antenna lead-in wire to take images to be transmitted to a television receiver; a radio-frequency converter circuit that converts video signals generated from the images by the surveillance cameras into radio-frequency signals, wherein the radio-frequency signals corresponding to the images taken by the surveillance cameras are transmitted through the antenna lead-in wire to the television receiver; a power supply control circuit that permits power supply to each of the surveillance cameras and transmission of radio-frequency signals to the television receiver when a significant change in each location under surveillance is detected; and a warning generation device that receives the radio-frequency signals, evaluates a level of radio-frequency signals for each channel corresponding to each of the surveillance camera, and generates a warning. 14. A surveillance system according to claim 13, wherein the warning generation device includes:a signal level determination circuit that is provided for each channel to evaluate the level of the radio-frequency signals for the channel inputted through a filter provided for each level of the radio-frequency signals; and a warning generation circuit that is provided for each signal level determination circuit to generate a warning when radio-frequency signals having the level corresponding to the signal level determination circuit are inputted. 15. A surveillance system according to claim 13, wherein the warning generation device includes:a signal level determination circuit that evaluates the level of the radio-frequency signals inputted through a variable frequency filter; a channel scanning circuit that determines a channel corresponding to the level of the radio-frequency signals; one or more of warning generation circuits that is provided for each channel to generate a warning when receiving the radio-frequency signals; and a selector that receives determination results of the signal determination circuit and the channel scanning circuit, and supplies the output of the signal determination circuit to at least one of the warning generation circuits corresponding are to the channel.