Current Direction recognition is a feature that helps to positively identify a line at points distant from the application of the signal. It is highly desirable, if not essential, for positive identification of long distance lines. These lines can be traced and positively identified through congested areas or when running parallel to other lines.
The CD feature on the RD8200 locators indicate the direction of the current flow on a line. Identity of the target line is established if the locator display indicates that the current is flowing forward and away from the point of application of the transmitter signal.
A signal that has coupled onto adjacent lines finds a return path to the point of the original signal application. This is indicated by the locator arrow pointing back towards the transmitter.
This is in contrast to the forward pointing arrow indicating the target line.
The CD transmitter signal should be directly coupled to the target line with a remote ground connection. Most CD signals are low frequency, making them unsuitable for connection with a normal clamp or induction. These can however be applied with a transmitter CD clamp.
Using Current Direction (CD) to aid line identification
The RD8200 locators, and Tx-10 and Tx-10B transmitters feature several CD frequencies to help you determine the direction of current through a target line.
NOTE: The transmitter and locator must both have the same CD frequency or frequencies installed to enable the feature to be used. If you have more than one CD frequency installed ensure that the transmitter and locator are both set to the same CD frequency. CD frequencies on both the locator and transmitter will be denoted by the 
icon on the display.
Current Direction
To select the CD frequency, proceed as follows:
Transmitter
- Switch the transmitter off.
- Connect the transmitter to target cable or pipe, either by Direct Connection or by using a CD clamp.
- Switch the transmitter on.
- Press the
key until the CD frequency is displayed.
CD is a combination of two frequencies, a CD frequency and a locate frequency.
Locator
- Press the key until the CD frequency is displayed, indicated by the icon.
4 kHz CD
RD8200 models feature Current Direction using a 4 kHz frequency. This frequency is designed to enable you to use CD to identify a target line on higher impedance cables such as telephone cables and CATV.