PURPOSE: To communicate messages in one direction between slave machines by disconnecting a telephone line and a line connection part by a switching part to short-circuit the line connection part side at the time of the message mode.
CONSTITUTION: A switching part 9 not only disconnects the telephone line and a line connection part 3 but also shortcircuits the side of the line connection part 3. Consequently, the telephone line side and the internal circuit side are disconnected in the line connection part 3 to complete the preparation for message communication. That is, impedance matching on the telephone line side viewed from the line connection part 8 is considerably broken when the input side of the line connection part 3, namely, the two-wire side of a two-wire/ four-wire conversion circuit in the line connection part 3 is short-circuited, and therefore, the extent of echo attenuation on the four-wire side (the internal circuit side) of the two-wire/four-wire conversion circuit is minimized and the signal from a reception part is leaked to the transmission part side. Thereafter, message communication from a slave machine B to a slave machine C is started. Thus, message communication between slave machines is possible.
SEO MASAYOSHI
ONO KOJI
TODA MANABU
