First, ask the previous owner if the system is currently monitored. If it is and you do not intend to secure a monitoring agreement, ensure the previous owners have canceled their service before your phone system is turned on. If you plan on securing a monitoring contract, contact the alarm company for proper training and activation of the system. If this is not done, the monitoring company will not be able to verify your right to be in the home and they will have to request a law enforcement dispatch each time you accidentally set off the system.
Secondly, the previous owner should have provided you with security company information. If not, you will need to contact the security company that installed the system for power-down instructions.
Finally, if the previous owner did not cancel service before moving out, please be advised that you may have to present proof of ownership before the security company will assist you. The security company needs to be sure that they are dealing with a person, who has the legal right to shut the system down, and not a burglar.