Multi-channel measurement equipment enters or performs a special mode of operation in response to an arbitrarily chosen probe being momentarily touched to a special terminal. A signal identifiable by its uncommon properties is present at the special terminal. The uncommon signal is generated by a suitable circuit, which may be similar to a pseudo random sequence generator. Each channel is equipped with a recognition circuit that recognizes the presence of the uncommon signal. The recognition circuits each receive a copy of the uncommon ID signal, and the task of recognition is performed by pattern matching over time. To enter or perform the special mode the operator touches the probe to the special terminal. After a suitable but brief period of time the recognition circuit for that probe produces an output that indicates recognition. The measurement equipment responds by entering or performing the special mode of operation. The special mode of operation may be ended by touching again touching the probe to the special terminal, by some other manual action, such as a keystroke or mouse click, or by some other event within the context of the special mode.