Patent ID: 7868781

Claim:
An encoder, comprising: a position detection part for detecting a signal corresponding to a position of a specimen and for calculating said position of said specimen; and a communication device for transmitting information on said position to a host machine connected via a communication line, said communication device having: a two-way communication mode for receiving command data from said host machine, and, when said command data is a two-way communication request command, transmitting said position information requested by said command data to said host machine; a one-way communication mode for executing one-way transmission processing for transmitting said position information to said host machine at a prescribed communication cycle, when said command data received in said two-way communication mode is a one-way communication request command; and a quasi one-way communication mode for executing quasi one-way transmission processing for transmitting said position information to said host machine for only a prescribed number of transmissions at a prescribed communication cycle when said command data received in said two-way communication mode is a quasi one-way communication request command, and thereafter, waiting only a prescribed time to receive said command data, and transitioning to said two-way communication mode when said command data is received, and repeating said quasi one-way transmission processing when said command data is not received.