The 5-Watt and 10-Watt transmitters from Vivax-Metrotech have a special “SD” (Signal Direction) frequency in them as a standard frequency. This feature is used to verify if the line being located is the target to which the transmitter has been connected. When a transmitter is connected to a target line, the signal travels along it and finds the easiest way to travel back, usually via the ground and ground stake. However, very often the signal will travel back along adjacent cables or pipes as these can offer an easier route.
As a result, there can be multiple signals radiating from cables and pipes in the area making it difficult to identify the target line. These return signals are typically traveling in the opposite direction than the applied signal. The Signal Direction feature identifies which direction the signal is flowing and hence the target line.
When using a receiver with the SD feature the LCD on the receiver will show a directional arrow. This arrow will point away from the location of the transmitter to show that you are on the correct cable. If the arrow on the receiver LCD is point towards the transmitter, this means that you are on a line that has bleed off returning back to the ground.
Receiver SD Upgrades are available for the vLoc3-Pro, vLocPro2 and vLocML2+