An ultrasonic surgical instrument , comprising: (a) a first modular assembly , including: (i) at least a portion of an end effector configured to manipulate a tissue; (b) a second modular assembly configured to mechanically couple with the first modular assembly in a predetermined alignment relative to each other, wherein the second modular assembly includes: (i) a body assembly configured to support an ultrasonic transducer ; (ii) a transducer power circuit configured to electrically connect to the ultrasonic transducer and a generator , and (iii) an activation switch electrically connected to the transducer power circuit , wherein the activation switch is configured to selectively power the ultrasonic transducer by directing electrical power from the generator to the ultrasonic transducer with the first and second modular assemblies in the predetermined alignment, and characterised in that the ultrasonic surgical instrument further comprises (c) an electrical lockout electrically connected to the transducer power circuit , wherein the electrical lockout is configured to inhibit the activation switch from powering the ultrasonic transducer with the first and second modular assemblies misaligned from the predetermined alignment such that the first and second modular assemblies are in a locked-out state, and wherein the electrical lockout is further configured to allow the activation switch to power the ultrasonic transducer with the first and second modular assemblies in the predetermined alignment such that the first and second modular assemblies are in an operational state. (a) a first modular assembly , including: (i) at least a portion of an end effector configured to manipulate a tissue; (i) at least a portion of an end effector configured to manipulate a tissue; (b) a second modular assembly configured to mechanically couple with the first modular assembly in a predetermined alignment relative to each other, wherein the second modular assembly includes: (i) a body assembly configured to support an ultrasonic transducer ; (ii) a transducer power circuit configured to electrically connect to the ultrasonic transducer and a generator , and (iii) an activation switch electrically connected to the transducer power circuit , wherein the activation switch is configured to selectively power the ultrasonic transducer by directing electrical power from the generator to the ultrasonic transducer with the first and second modular assemblies in the predetermined alignment, and characterised in that the ultrasonic surgical instrument further comprises (i) a body assembly configured to support an ultrasonic transducer ; (ii) a transducer power circuit configured to electrically connect to the ultrasonic transducer and a generator , and (iii) an activation switch electrically connected to the transducer power circuit , wherein the activation switch is configured to selectively power the ultrasonic transducer by directing electrical power from the generator to the ultrasonic transducer with the first and second modular assemblies in the predetermined alignment, and characterised in that the ultrasonic surgical instrument further comprises (c) an electrical lockout electrically connected to the transducer power circuit , wherein the electrical lockout is configured to inhibit the activation switch from powering the ultrasonic transducer with the first and second modular assemblies misaligned from the predetermined alignment such that the first and second modular assemblies are in a locked-out state, and wherein the electrical lockout is further configured to allow the activation switch to power the ultrasonic transducer with the first and second modular assemblies in the predetermined alignment such that the first and second modular assemblies are in an operational state. <EOS>