  We study radio and X-ray emissions from IMBHs and explore the unified model
for accretion and ejection processes. The radio band survey of IMBH (candidate)
hosted galaxies indicates that only a small fraction ($\sim$0.6\%) of them are
radio-band active. In addition, very long baseline interferometry observations
reveal parsec-scale radio emission of IMBHs, further resulting in a lower
fraction of actively ejecting objects (radio emission is produced by IMBHs
other than hosts), which is consistent with a long quiescent state in the
evolution cycle of IMBHs. Most (75\%, i.e., 3 out of 4 samples according to a
recent mini-survey) of the radio-emitting IMBHs are associated with radio
relics and there is also evidence of dual radio blobs from episodic ejecting
phases. Taking the radio emission and the corresponding core X-ray emission of
IMBH, we confirm a universal fundamental plane relation (FMP) of black hole
activity. Furthermore, state transitions can be inferred by comparing a few
cases in XRBs and IMBHs in FMP, i.e., both radio luminosity and emission
regions evolve along these state transitions. These signatures and evidence
suggest an analogy among all kinds of accretion systems which span from stellar
mass to supermassive black holes, hinting at unified accretion and ejection
physics. To validate the unified model, we explore the correlation between the
scale of outflows (corresponding to ejection powers) and the masses of central
engines; it shows that the largest scale of outflows $\hat{LS}_\mathrm{out}$
follows a power-law correlation with the masses of accretors $M_\mathrm{core}$,
i.e., $\log{\hat{LS}_\mathrm{out}} = (0.73\pm0.01)\log{M_\mathrm{core}} -
(3.34\pm0.10)$. In conclusion, this work provides evidence to support the claim
that the ejection (and accretion) process behaves as scale-invariant and their
power is regulated by the masses of accretors.
