Multiway switching#Carter system
The Hamburg circuit (english Carter system) is a special form of the savings -way circuit in the electrical installation. She's in Germany according to DIN VDE 0100-460 Section 465.1.2 and DIN VDE 0100-550, section 5 and in the United States according to the National Electrical Code since 1923 (currently: NEC Article 404.2 ) not in newly installed or in old and advanced low-voltage systems permissible because the neutral conductor must not be connected single-pole (VDE 0100-460 ). Single-pole change-over switch in an AC circuit must be connected to the same phase conductors ( VDE 0100-550, see explanatory note to Section 5).
The danger of the Hamburg circuit is that it is switched off at lights with missing protection against contact ( older design ) can the lamp thread abut the potential of the outer conductor. Thus, a person can when you touch the lamp thread suffer a fatal electric shock ( when changing a light bulb, for example ). Furthermore, during the switching process with inappropriate exchange switches a short circuit between phase and neutral conductors is possible.
Hamburger circuits in old (built prior to May 1973) are still kept in effect when they were built according to the standards in force at the date of the establishment and if it does not change is made. This particularly relates to the replacement of the rotary switch previously used and suitable for the Hamburg circuit with new rocker switches.
Installation and use
The Hamburg circuit was used to
- With a single conductor per switching to light to enable a two-way circuit, starting from positions where the neutral conductor and outer conductor were already available.
- To lay lines with fewer cores (eg NYM 4 x 1.5 mm ² instead of a NYM 5 x 1.5 mm ²).
- Lines that contain too few veins, to use yet for an AC circuit.
The special ( and danger ) of the circuit is that the lamp was placed in the Corresponding single.
With only a four-wire connection between two exchange counters each additional sockets could be attached to both switches. The conductors were required in this case, the only Corresponding ( Corresponding is the name of the connection cable (s) between two AC switches), the outer conductor, the neutral conductor and the protective conductor. The necessary in a conventional switching circuit has second corresponding savings.