Abstract: A multiplex transmission system includes a plurality of multiplex nodes interconnected by a common multiplex transmission line. Data frames are transmitted among the multiplex nodes through the multiplex transmission line. A data frame transmitted from a sending multiplex node includes a data area which is divided into subdivided areas in accordance with data transmitted therefrom and data transmitted from receiving multiplex nodes which send data in response to a send request, in accordance with the number of data pieces or the number of bits, and the receiving nodes send data to respective subdivided areas in a predetermined order, to thereby carry out a data transmission. Accordingly, the sending multiplex node can simultaneously collect data from the receiving multiplex nodes which are functionally subordinate. When any of the receiving multiplex nodes fails to return an ACK signal, the sending multiplex node retransmits the data frame.

Abstract: An electronic component testing laminated board suitable for performing a heat test on electronic components of a multikind and small quantity production type. The laminated board includes a metal plate, a testing circuit layer including a double-sided printing wiring board or the like and integrally formed through a thin electric insulating layer on one side of the metal plate for mounting thereon electronic components to be tested, and a heater circuit layer including a metal foil circuit or the like and integrally formed through another electric insulating layer on the other side of the metal plate for maintaining the testing circuit layer at a given temperature. An inorganic filler or the like is added to the electric insulating layers. An electronic component testing box for removably accommodating the electronic component testing lamianted board includes walls made of a heat insulating material, power supply connecting connector, signal input and output connector, temperature measuring apparatus, etc.