If you need to check the physical layer status and the quality of digital circuits then there are two tools which you are likely to need. The first is a breakout box which can be used to determine the connection integrity between the DTE and the DCE. This box (also know as ‘BOB’) has two external connections which can be extended on the DTE and DCE.
The box supplies status information on the digital circuit and will also display any data being transmitted at the time. The device will normally display real-time status information about data, clocking, space and activity. On most of the breakout boxes, this information is displayed using status LEDs. It is normally quite a compact device powered by batteries in order to increase it’s portability. The box contains buffered electrical circuitry which does not interfere with the actual line signal during testing, Most are also capable of verifying the electrical resistance and line voltage too.
These are focused on physical problems on a network primarily, although errors can occur for other reasons. If you’re looking at other issues perhaps conflicts on a proxy IP address or an application error then you should look at other tools.
The second piece of equipment you’ll need has a variety of names but is most commonly known as BERT. This stands for bit-error-rate tester and is actually a lot more sophisticated piece of kit. This can effectively measure the error rate in a digital signal. This error rate can be measured both from end to end circuit or on a portion of a circuit for isolating individual faults. The bit error rate is often measured during installation and commissioning so that it can be used as a baseline.
The BERT also is used to measure error rates on the variety of different bit patterns that it can generate. You can use this information for timing or noise issues on the circuit. It does take time but allows a line to be monitored accurately and a traffic and error analysis can be performed