Choke-collar
this restraining device was used to control an individual, most often a slave. Once the collar was secured around the being's neck, it was impossible to remove without the proper access code. The master could control the collar with a small remove, causing it to constrict at the touch of a button. If the wearer got too far from the control unit, the collar would recognize that it was no longer in range and begin constricting. The remote controls of many collars were also equipped dead-man switches, which would immediately signal the collar to start constricting if the master holding the remote was killed.