Basic Level Crossing CCTV Notes. Page one of five

Transcription

1 Page one of five Relays (PIC) SR (PIC) R (CC) SR (MON OFF) R (MON) R (CAM) PR (DAY) R (NIGHT) R (CAM OFF) R Normally energised, cameras on standby, pressing picture button deenergisers it and picture is displayed. Pulling picture button re-energises relay and cancels picture unless the lower sequence has been started. UP KR lost will automatically call a picture (unless on local control). Pressing crossing clear will cancel picture as long as DN KR is energised. AUTO/MAN button set on manual will keep the picture on until raise button pressed. Repeat relay of (PIC) SR Energised by crossing clear button being pressed only if picture is called (PIC) SR de-energised and DN KR is energised (barriers down). Centre position of three position MONITOR switch, it energises relay and cuts feed off to both monitors. (Other two positions of MONITOR switch); Left: de-energises relay and feeds BX/NX110 supply to monitor one. Right: picks relay and supplies BX/NX110 supply to monitor two. Controls which camera is being fed (power and standby). Energised: Camera TWO : Camera ONE For Floodlighting (and no longer used IRIS). Energised will turn off floodlights and lose feed to IRIS. Used instead of (DAY) R. Energised will turn on floodlights and provide feed to the no longer used IRIS. Cuts feed to both cameras when energised. Note: in the event of power failure, monitor one and camera one are selected by default. Some signalboxes have only one monitor.

2 Page two of five (VIDEO) R (NOR) R Most crossing CCTV systems use a single COAX cable for both pictures (one at a time), this relay decides which is to be transmitted. : Camera ONE Energised: Camera TWO This relay is de-energised when barriers are taken on local control. Both cameras are powered up but PIC circuit feed is cut off. Switches and relay position SWITCH/BUTTON POSITION Relay position MONITOR CAMERA PICTURE OFF POSITION 1 POSITION 2 OFF POSITION 1 POSITION 2 NORMAL (not pressed or pulled) PRESSED and released (MON OFF) R energised, cuts BX/NX110 feed to monitors. (MON OFF) R de-energised, provides feed to monitor. (MON) R de-energised will select monitor 1. (MON OFF) R de-energised, provides feed to monitor. (MON) R energised will select monitor 2. (CAM OFF) R energised. Feed cut off to both cameras. (CAM OFF) R de-energised. (CAM) R de-energised. (CAM) PR de-energised. Camera one powered up. (CAM OFF) R de-energised. (CAM) R energised. (CAM) PR energised. Camera two powered up. (PIC) SR and (PIC) R energised. No camera called but both on standby and powered up. (PIC) SR and (PIC) R de-energised. Picture called. Will cancel when crossing clear is pressed. PULLED and released (PIC) SR and (PIC) R energised. Picture cancelled.

3 Page three of five Test Facilities Most CCTV locations have a test facility to enable technicians to see how good the picture is from the camera before being sent to the signalbox. Using the correct connection and power socket (110v AC) plug in the monitor and select TEST button and the camera you are testing. On crossings with (VIDEO) R relays only the camera that is NOT in use by the signaller can be displayed on the test monitor. The signaller has over-riding function so he can change over the picture at any time. On other crossings where there are two sockets to monitor either picture, there is nothing preventing either picture being called as this is done via the switches on the test panel. Transmission The CCTV signal is sent down type A COAX cable via a modulator. Each modulator has its own set frequency which is determined by a crystal installed internally. At the end of the COAX at the signal box there is a demodulator, this also has to be the same frequency as the modulator. Both have a red LED which illuminates to state if the carrier (the signal) has reached that point. At the rear of each modulator/demodulator there is a video output socket to enable a test monitor to be plugged in. At certain locations along the line depending on the length of the COAX, a repeater (or Booster) location is provided with additional modulator, line amplifier and launch amplifier for the signal to be amplified if the signal box is far away. These repeaters are limited to seven in total. At each end of the COAX and repeater locations surge protection units must be fitted to protect from primarily lightning strikes. Normal position of relays (Barriers lowered and indicated, and crossing clear button depressed**) Relay (PIC) SR (PIC) R (CC) R (MON) R (MON OFF) R (CAM) PR (NOR) R (DAY) R (NIGHT) R (CAM OFF) R (VIDEO) R **(CC) R Position Energised Energised Monitor 2 on Monitor 1 on Energised Camera 2 selected Camera 1 selected Both dependant on general lighting and weather conditions Energised Camera 1 transmitting Energised Camera 2 transmitting (PIC) SR & (PIC) R both now re-energised, picture no longer displayed.

4 Differing circuitry Basic Level Crossing CCTV Notes Page four of five The picture calling sequence is basically the same as above. Instead of one relay, the (CAM) PR selecting which camera is to be powered up and called, they have their own relays as follows; Camera switch at signal box is still CAM 1 OFF CAM 2, however, at the CCTV location there is: (CAM 1) R, (CAM A) R, (CAM 2) R and (CAM B) R as additional relays. Camera 1 selected (CAM A) R de-energised (CAM B) R energised Camera 2 selected (CAM A) R energised (CAM B) R de-energised. These relays provide the feed and put both cameras into standby mode. Two further relays, (PIC 1) and (PIC 2) at the CCTV location call the picture up. (TEST 1) R & (TEST 2) R are provided to prevent the signaller losing his picture when the technician is using a test monitor. The relay circuitry differs at various locations, so the diagrams at each crossing should be consulted. Setting-up the lens on a Grundig Style Camera The Grundig camera has several adjustment s on it to get the best picture focus and also IRIS settings too. FOCUS: On the top at the front just before the lens there is a black protective cap approx 12mm long, this is for focusing the camera. By turning the serrated knob either clockwise or anti-clockwise it will adjust the focus. ALC: Automatic Light Compensation. On the lens itself there are two tiny adjusting screws beneath two plastic protective caps. The LH screw is the ALC, this stands for Automatic Light Compensation. This sets the IRIS reaction time fast or slow for changing light conditions. Adjustment towards peak (Pk), will increase sensitivity and reaction time, towards average (Av) will decrease both. Set to mid-range for most applications. You will not see a major change when adjusting.

5 Page five of five (IRIS) LEVEL: This is the main IRIS control, adjusting towards H (high) will open the IRIS, making picture brighter, and towards L (low) will close it, making it darker. After initial set up, the IRIS will maintain this level in a variety of lighting conditions. Set-up should be performed during daylight as night-time set up will commonly cause the IRIS to remain far too open during the day. Both ALC and LEVEL are factory set and usually do not need adjusting on site. Both styles of cameras are 12-15v DC via a small transformer which is 110v AC. The Plettac camera gets its supply via the multi-pin connector. The red and green wires are for voltage free switching purposes. Setting-up the lens on a Plettac Style Camera Plettac cameras are fully automatic for the IRIS settings. The focus and lens angle are adjustable on the lens itself by small thumb screws which are loosened to adjust by rotating and then retightened to maintain setting. The Plettac model FAC 858 is used at crossings, and the FAC 858 NRF is used for tail-lamp sites as these have special filters to show true red tail lights during the night. Faulting The camera circuit is complex for a simple function and therefore many things can go wrong. When called to a fault with the CCTV, depending on which end you go to first, check the basics, i.e. if the signaller cannot get a picture, is the monitor turned on? Is the picture button registering a press? Maybe disconnect the UP KR and see if the picture comes on automatically, this may point to a faulty picture button. Is the brightness on the monitor turned down? Can you swop to another crossings monitor? Is it night time and has the floodlighting failed making the screen look dead? If the system is on camera 2 but camera 1 is displaying, this is the default setting, so has a relay not picked or loss of power? The same if camera 2 cannot be selected. If at the CCTV location end, plug in a test monitor to eliminate the actual camera. Check the red LED s on the modulators. Spares are scarce so unfortunately you will need to narrow the fault down before correct faulty part is sought. Hopefully the relay functions and sequence above will help you narrow the fault down. This is an uncontrolled document and is not endorsed by Network Rail, it is NOT for testing, commissioning, or maintenance purposes. By F. M. Spowart Retford S&T Jun 14 Ver2