referring to fig4 and 5 , the preferred embodiment of a monitoring device of power line and camera mounted on a vehicle 10 , comprises a cable line 11 installed within the vehicle 10 , and electrically connected to a power system 12 of the vehicle 10 to form a first power line 13 . the first power line 13 has both ends respectively and electrically connected to a radio frequency transmitter 30 and a radio frequency receiver 50 . the first cable connector 70 and second cable connector 71 are arranged at a junction of the first power line 13 to separate a tractor 101 and container 102 of the vehicle 10 for reducing the correlation between the location of the radio frequency transmitter and radio frequency receiver 30 , 50 , and enhancing independence . the vehicle 10 has a screen host 40 and a first camera 20 respectively arranged at a front end and rear end thereof . the radio frequency transmitter 30 has an input end electrically connected to the first camera 20 and an output end electrically connected to the first power line 13 , and the radio frequency receiver 50 has an input end electrically connected to the first power line 13 and an output end electrically connected to the screen host 40 so that the first power line 13 supplies power for the radio frequency transmitter and radio frequency receiver 30 , 50 for transmitting radio frequency signal 60 , and the first power line 13 also supplies power for the first camera and screen host 20 , 40 . in the embodiment , the first camera 20 takes a first object 22 to capture a first image signal 21 ; the radio frequency transmitter 30 is electrically connected to a second camera 23 to take a second object 25 and capture a second image signal 24 , and the second camera 23 is embedded in a rearview mirror 103 of the vehicle 10 . as a result , the radio frequency transmitter 30 transmits the first image signal or second image signal 21 , 24 to the first power line 13 , and the first power line 13 as a medium receiving the first image signal 21 from the radio frequency transmitter 30 and transmitting the signal to the screen host 40 . corresponding to the above features , the power line 13 is electrically connected to a second power line 90 , and the second power line 90 is electrically connected to a driving video recorder 91 . the driving video recorder 91 is electrically connected to a third camera 92 which takes a third object 94 to capture a third image signal 93 for being transmitted to the screen host 40 and being recorded un the driving video recorder 91 . further , the power line 13 is electrically connected to the second power line 90 for the first image signal or second image signal 21 , 24 to be transmitted to the second power line 90 , and recorded to the driving video recorder 91 . with the reference fig6 , the radio frequency transmitter 30 has a first circuit module 31 , and the first circuit module 31 has a modulator 311 , a first oscillator 312 , a first operational amplifier 313 , and a first capacitor 314 ; the first image signal or second image signal 21 , 24 is modulated into high frequency signal 315 by the modulator 311 , transmitted to the first oscillator 312 to produce periodic sinusoidal wave signal , and then amplified by the first operational amplifier 313 to be transmitted to the first capacitor 314 for signal coupling 61 , and finally the signal is transmitted to the first power line 13 . further , the first power line 13 in parallel is electrically connected to a first pulse - width modulation 32 and second pulse - width modulation 33 to respectively send voltage of 5 volts ( v ) to the first circuit module 31 , and voltage of 12 volts ( v ) to the first camera 20 for controlling voltage and supplying power for the first camera 20 or the second camera 23 , and the first circuit module 31 . with the reference fig7 , the radio frequency receiver 50 has a second circuit module 51 , and the second circuit module 51 has a demodulator 511 , a frequency mixer 512 , a second oscillator 513 , a surface filter 514 , a second operational amplifier 515 , a third operational amplifier 516 , a forth operational amplifier 517 , and a second capacitor 518 ; the high frequency signal 315 is transmitted to the first power line 13 and the second capacitor 518 for signal coupling , amplified by the second operational amplifier 515 , and then transmitted to the second oscillator 513 to produce periodic sinusoidal wave signal ; at the same time , the amplified signal and sinusoidal wave signal are mixed by the frequency mixer 512 to form intermediate frequency signal 519 ; the signal is amplified by the third operational amplifier 516 , transmitted to the surface filter 514 for noise filtering , and then amplified by the forth operational amplifier 517 to be transmitted to the demodulator 511 for the intermediate frequency signal 519 being demodulated into the first image signal or second image signal 21 , 24 , and finally the signal is transmitted to the screen host 40 . further , the first power line 13 in parallel is electrically connected to a third pulse - width modulation 52 and forth pulse - width modulation 53 to respectively send voltage of 5 volts ( v ) to the second circuit module 51 , and voltage of 12 volts ( v ) to the screen host 40 for controlling voltage and supplying power for the screen host 40 and the second circuit module 51 . with the reference to fig8 and 9 , the first camera 20 , second camera 23 , and third camera 92 is respectively arranged at the rear end of the vehicle 10 , embedded in a rearview mirror 103 of the vehicle 10 , and arranged at the front end of the vehicle 10 to form a monitoring region c right behind the vehicle 10 , monitoring regions a and b rearward extending from the right and left perspective view , and monitoring region d right in front of the vehicle 10 . the image signals 21 , 24 , 93 captured by the above cameras 20 , 23 , 92 can be recorded by the driving video recorder 91 for driver &# 39 ; s accident record in order to clarify the attribution of liability . based on the features disclosed , the present invention integrates wireless signals , cable signals , and power to transmit image signals by power transmission . the present invention also provides single power line for each camera so that any of the cameras can be set at any position of the vehicle 10 to monitor the objects around the vehicle 10 . although particular embodiments of the invention have been described in detail for purposes of illustration , various modifications and enhancements may be made without departing from the spirit and scope of the invention . accordingly , the invention is not to be limited except as by the appended claims .