A modular surgical system is disclosed. The modular surgical system comprises a header module, a first surgical module, a second surgical module, and a module identification circuit. The second surgical module is arrangeable in a stack configuration with the header module and the first surgical module. The module identification circuit is configured to cause a pre-determined current to be transmitted to the first surgical module through the second surgical module in the stack configuration, detect a first voltage indicative of a first position of the first surgical module in the stack configuration, and detect a second voltage indicative of a second position of the second surgical module in the stack configuration. The second voltage is different than the first voltage.