Collision model and communication strategy of multiple callings

The circuit and topology of RS232C interface are analyzed to reveal the mechanism of multiple callings from terminals. Poisson distribution is introduced to describe the calling process and develop the collision model. A collision probability depends on calling frame format, baud rate and calling frequency. The collision probability of calling from two or more terminals is less than 0.01% when mean calling frequency is less than 10 times per second. The collision can be listened, identified and compensated with another calling, whose collision probability is less than 0.0001%. It is showed that the communication strategy of multiple terminals calling to central computer with RS232C protocol is feasible.