A signature verification pen has been developed by IBM Corporation. The purpose of the pen is to authenticate the person who provides the signature by detecting whether the user is forging someone else's signature. The instrumented pen has analog sensors. Sensor signals are conditioned using microcircuitry built into the pen and sampled into a digital computer at the rate of 80 samples/s using an ADC. Typically, about 1000 data samples are collected per signature. Prior to the pen's use, authentic signatures are collected off-line and stored in a reference database. When a signature and the corresponding identification code are supplied to the computer for verification, a program in the processor retrieves the authentic signature from the database, by referring to the identification code, and then compares the two sets of data for authenticity. This process takes about 3 s. Discuss the types of sensors that could be used in the pen. Estimate the total time required for a signal verification. What are the advantages and disadvantages of this method in comparison to having the user punch in an identification code alone or provide the signature without the identification code?