er (GM) with a frequency input. This input reference is usually a signal such as 10 MHz, 2 MHz, synchronous Ethernet (SyncE), or some E1/T1 time-divi- sion multiplexing (TDM)-based circuit from a synchronization supply unit (SSU) or building integ- rated timing supply (BITS). The most basic thing to ensure is that the cable and connectors are cor- rect, and the following section looks at them in some detail. Use of the terms "master" and "slave" is ONLY in association with the official terminology used in industry specifications and standards, and in no way diminishes Pearson's commitment to promoting diversity, equity, and inclusion, and challenging, countering, and/or combating bias and stereotyping in the global population the learners we serve. There are many, many types of connectors, and several look very similar to each other. In fact, it is quite easy to plug one connector into the other and damage them both, since they are "almost" com- patible, but not quite. Avoiding this damage requires the engineer to be very diligent about under- standing what connections are needed and what type they are-the authors cannot stress this enough. About 95% of the time, the first big issue with any new timing project is finding the correct connectors and cables for the timing input/output signals. The next consideration is to confirm whether the connector is male or female. The timing engineer is advised to always carry a few gender bender adapters that allow male-to-male and female-to- female connections in case the cables do not match gender. The following are the major connector types commonly found for these forms of input: Bayonet Neill-Concelman (BNC): BNC connectors are very common on PRC/PRS devices and equipment that tests timing or anything that needs a frequency input. BNC connectors are often used to carry 10-MHz/2-MHz signals and can be used to carry unbalanced 75-ohm E1/T1 signals (more on that in a moment). BNC connectors come in 50-ohm and 75-ohm versions, with the related cable type matching the impedan