Rotation information transmission apparatus

A rotation information transmission apparatus, comprising:

• a first substrate where a first coupler in arc form is provided in an upper portion or a lower portion;
• and
• a second substrate comprising a second coupler in arc form that is arranged in a location where coupling with the first coupler in arc form is possible and a third coupler in arc form, wherein
• the first coupler in arc form is a single coupler in arc form comprising a signal line in arc form and a feedback path in arc form where one end of the signal line and one end of the feedback path are connected to each other through a terminal resistor or a short-circuiting conductor,
• the length of the arc of the second coupler in arc form and the third coupler in arc form is shorter than the length of the arc of the first coupler in arc form,
• at least either the second coupler in arc form or the third coupler in arc form always couples with the first coupler in arc form,
• either the first substrate or the second substrate is fixed to a non-movable portion, and
• the other of the first substrate or the second substrate is fixed to a rotational member so as to be rotatable.