Support for as many as 127 devices and daisy-chaining of peripheral devices with up to 5 meters cable length are benefits of a jack-and-plug connector range for the USB. Other key features include plug-and-play compatibility, hot-swapping with dynamic connection and disconnection, ease of computer/telephony integration and port consolidation. Specs include transfer rates up to 12Mbit/s with a sub-channel for 1.5-Mbit/s signaling. Data transfer can be isochronous or asynchronous, and built-in power distribution is provided for low-power devices. The connectors come in series A (rectangular) and series B (square) formats, as well as dual-stack versions. Voltage rating is 30V ac and current rating is 1A/contact.