| 摘要 |
A method of checking the presence of mobile stations (DMRU:2, 500) communicating on a direct mode channel. The method comprises the steps of: a) sending (302) a presence inquiry message (106) provided with an identity from a first mobile station to a second mobile station (DMRU:2) on the direct mode channel, b) receiving said presence inquiry message at the second mobile station (DMRU:2), c) comparing the identity contained in said presence inquiry message (106) with the identity of the second mobile station, d) if the comparison shows that the identities are identical, sending an acknowledgment (107) containing the identity of the second mobile station from the second mobile station to the first mobile station on the direct mode channel, and e) indicating the result of the presence inquiry to the user (101) of the first mobile station.
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