def undbm(p, z=50):
    """Calculate the RMS voltage equivalent of a power ``p`` expressed in dBm.

    .. math::

        V_{\\mathrm{RMS}} = \\sqrt{z\\ 10^{p/10 - 3}}

    **Parameters:**

    p : scalar or sequence
        The power to be converted.

    z : scalar, optional
        The normalization resistance value, defaults to 50 ohm.

    **Returns:**

    Vrms : scalar or sequence
        The RMS voltage corresponding to ``p``.

    .. seealso:: :func:`undbp`, :func:`undbv`, :func:`dbm`, :func:`db`

    """
    iform = save_input_form(p)
    p = carray(p)
    up = np.sqrt(z*10.**(p/10.-3))
    return restore_input_form(up, iform)
dataset/ETHPy150Open ggventurini/python-deltasigma/deltasigma/_undbm.py/undbm/original