Local area network eleveator communications network

Claim 1

An elevator communications unit for use in an elevator communication system which includes a plurality of said communication units distributed among a building bus, a group bus, and a car bus, comprising: A transceiver machine responsive to a data signal in parallel form provided from an applications layer for converting said data signal from parallel form to serial form and providing a serial data signal onto a dual bus of said elevator communications system wherein said data signal is precede on said dual bus by a control byte signal for identifying whether communications of the data signal are local to the dual bus or directed to a remote bus (group or building), a message identifier signal, and a preamble signal, and a bus jam signal if said data signal is being provided onto an idle dual bus; a receive machine responsive to said serial data signal on said dual bus for converting said data signal from serial form to parallel form, for selecting only one data signal from one bus based on said preamble, for identifying said data signal as associated with the bus of said receive machine by means of said control byte, and providing said data signal to said applications layer when the message identifier signal of the received data signal for matches with a message identifier signal associated with said applications layer; a slot timer for timing the transmission and reception of said data signals by said communication unit.