Not true about action potential recording:

For typical action potential recording (which is also known as monophasic action potential), one microelectrode is placed inside the nerve fibre and the other electrode on the outside surface For biphasic recording of action potential, both the exploring electrodes are placed on the outside surface of nerve fibre, and they are connected to a CRO (cathode ray oscilloscope) Compound AP is an algebraic summation of the all the monophasic recording of AP from a mixed nerve which contains different types of nerve fibres with varying diameter.