PURPOSE: To enable the call processing function to be tested without using any accessory by providing a means connecting a transmission control section and a reception control section, and the circuit connection part of the transmission control section and that of the reception control section.

CONSTITUTION: An automobile telephone exchange TX gives a specific control instruction to a radio base station controller CE to set a transmission control section CS1, the reception control section CR2 of a control line, a transmission control section VS1, the reception control section VR2 of a talking line to the call processing mode and to set a reception control section CR1, a transmission control section CS2 of the control line and a reception control section VS2 of the talking line to the simulation mode respectively. Further, a common control section CC drives relay contacts rl1∼rl8 to connect the control section VS1 to the section VR1, the control section VS2 to the section VR2, the control section CS1 to the section CR1 and the control section CS2 to the section CR2 respectively, thereby activating the control sections CR1, CS2, VR1 and VS2 as pseudo automobile telephone subscribers. Thus, the maintenance personnel of the exchange TX conducts the test of the call processing function of the controller CD and the call processing function of the exchange TX.