The LBT is a Bit Error Rate Tester for testing synchronous or asynchronous modems and other DCEs. Testing can be conducted over full duplex or half duplex links. The LBT can also test modems connected in multipoint configuration for polling operation. A network with up to 32 slave modems is supported. The LBT operates synchronously or synchronously at data rates from 75 bps to 38.4 kbps. When operating in synchronous mode, five test patterns are available: 511 or 2047 pseudo random, 7 space 1 mark, 7 mark 1 space, or alternating mark/space. In asynchronous and multipoint modes, only the 511 bit pattern is available.