A
system is provided for upgrading a legacy
security system having a legacy control panel and a legacy
card reader, without interfering with
legacy system operation. A new control panel is installed between the legacy
card reader and the legacy control panel. Also, a new token reader is installed next to the legacy
card reader and connected to the new control panel. The new control panel passes credentials it receives from the legacy card reader to the legacy control panel, avoiding interference with
legacy system operation. When the new control panel receives credentials from the new token reader, it evaluates them against an access rights
list administered independently of the legacy access rights
list. When the new control panel determines that an access request should be granted, it sends a memorized legacy credential associated with full access rights to the legacy control panel, causing it to open the door.