This part of IEC 63138, which is a sectional specification (SS), provides information and rules for the preparation of detail specifications (DS) for MQ4 series circular connector with four RF channels ÿas well as a detailed specification of the blank format. MQ4 series circular connector with 50 ohm nominal impedance has four RF channels which can be engaged and disengaged at the same time. There are two versions of plug connectors, one is quick lock version, the other is threaded version. The socket connector provides two coupling mechanisms, quick-lock and threaded coupling. MQ4 series circular connectors can be used in mobile communication system and other communication equipment. It also prescribes mating face dimensions and gauging information of MQ4 series circular connectors, and tests selected from IEC 63138, applicable to all detail specifications relating to MQ4 series circular connectors together with the pro forma blank detail specification. Note: Metric dimension are original dimensions. All undimensioned pictorial configurations are for reference purpose only.