PURPOSE: To take out the efficiently by incorporating a pinion and rudder in a rod and interlocking with accelerator operation to rotate a pinion thus to correct the functional rate of rod and the tuning of amplifier thereby tuning the variation of rotary force due to accelerator operation with turning of amplifier.

CONSTITUTION: A rudder 6 and pinion 7 are incorporated in a rod 5 and interlocked with the accelerator operation to rotate a pinion 7 thus to correct the functional rate of rod 5 and the turning of amplifier 3 and to tune the variation of rotary force due to accelerator operation with turning of amplifier 3. In other word, upon rotation of pinion 7 while interlocking with accelerator operation, the length of primary and secondary rods 1, 2 will vary while simultaneously the length between secondary detection rod 2 and amplifier 3 wil vary to cause variation of turining of amplifier 3. When reducing the output, for example, thrugh accelerator operation, the length of secondary detection rod 2 will increase to deflect the amplifier 3 toward speed reduction point A.