  IGR J17480$-$2446 is an accreting X-ray pulsar in a low-mass X-ray binary
harbored in the Galactic globular cluster Terzan 5. Compared with other
accreting millisecond pulsars, IGR J17480$-$2446 is peculiar in its low spin
frequency (11 Hz), which suggests that it might be a mildly recycled neutron
star at the very early phase of mass transfer. However, this model seems to be
in contrast with the low field strength deduced from the kiloHertz
quasi-periodic oscillations observed in IGR J17480$-$2446. Here we suggest an
alternative interpretation, assuming that the current binary system was formed
during an exchange encounter either between a binary (which contains a recycled
neutron star) and the current donor, or between a binary and an isolated,
recycled neutron star. In the resulting binary, the spin axis of the neutron
star could be parallel or anti-parallel with the orbital axis. In the later
case, the abnormally low frequency of IGR J17480$-$2446 may result from the
spin-down to spin-up evolution of the neutron star. We also briefly discuss the
possible observational implications of the pulsar in this scenario.
