by the shell of the connector, which may be reduced if it is left floating. An alternative solution is to connect the shell to pin 1 and the shield through a small value capacitor, providing RF shielding but allowing very little audio-frequency current to flow. This capability can be built into a fixed jack or a cable terminated with XLR connectors. The standard signal flow for audio in XLR connectors is that the output is a male connector and the input is female. In other words, the pins on the plug point in the direction of signal flow. This is the opposite of power connector standards which normally use female connectors for outputs, a convention influenced by the need to prevent accidental contact with dangerous voltages. However, the voltages of microphone and line level audio signals are not hazardous. The male XLR is usually incorporated in the body of a microphone. Since equipment often requires an input on a TRS phone jack or an XLR connector, Neutrik and Amphenol offer several models of combination connector that accept both XLR and TS or TRS phone plugs. Four-pin – DC power The most common standard is for pin 1 to be ground and pin 4 to be 12 volts (nominal), with pins 2 and 3 unused. This configuration is used on most professional video cameras and is also common on audio equipment designed for location use. There are other non-standard arrangements, particularly found on older equipment. Four-pin – intercom headset Clear-Com, Telex, RTS and many other production intercom systems use four-pin XLR connectors for attaching monaural intercom headsets or handsets. The standard pinout for four-pin XLR headsets is: Pin 1 = Microphone ground (screen/shield); Pin 2 = Microphone signal ("hot") input; Pin 3 = Headphone ground (return); Pin 4 = Headphone signal ("hot") output. Five-pin – DMX512 and DC power for audio systems The five-pin XLR is the standard connector for DMX512, the most common protocol for controlling professional lighting and related equipment. Three-pin XLR connectors are increasingly common instead. These are electrically compatible with a simple jumpering 1–1, 2–2, 3–3 between them. However, using three-pin XLR connectors for DMX512 is specifically prohibited by section 7.1.2 of the DMX512 standard. Five-pin XLR is also a common power connector in modular professional audio systems, such as the Automated Processes, Inc.'s (API) Lunchbox format. This format is becoming increasingly popular and five-pin XLR for