When an alarm system is locked, it means mainly two things, the panel can no longer accept onsite, or sometimes, even offsite programming modification by anyone other than the installing company.
Usually, locking a control panel is done for multiple reasons. Sometimes, it is done to a leased or rental system to protect the installing company's equity in the system, other times some companies do it to protect both the panel's programming integrity, as well as prevent account takeovers.
That said, systems are commonly locked out of programming or have the installer codes changed from default, even onsite programming disabled. It is a security concern, as well as a reasonable thing to do while a system is under contract.
However, upon termination of a contract, the ethical thing for an installing company to do is to "unlock" the panel, provide the installer code (not likely), or change the installer code to a factory default, as well as enable the onsite-programming feature.
When considering monitoring as well as professional installation, always ask what their policy is with the alarm panel and locking.
