Abstract: In apparatus for measuring the output power an RF transmitter stage (34) connected to an antenna (44) via a quarter wavelength stripline (38), a manual probe (20) is applied connect the output of the transmitter stage to a power meter (24) and connect the output end of the stripline (38) to ground. Thus, RF signals which were passed to the antenna (44) are switched to the power meter (24). All the circuitry including the antenna (44) is mounted on a printed circuit board (60) disposed within a housing (14) which has an aperture (18) to enable the probe (20) to be inserted. By providing a suitable meter, parameters other than RF power can be measured.

Abstract: A data entry keyboard apparatus includes a key switch array (18) in a keyboard unit (12) connected via a cable (14) to a tamper-resistant module (28) which contains control circuitry (16). The control circuitry (16) includes a random pattern generator (30) which generates successive random patterns, causing the selection of a single column and a random pattern of rows, thereby effecting the simulation of key actuations. An EXCLUSIVE-OR gating network (56a-56d) is effective to distinguish a genuine key actuation from simulated key actuations. The invention prevents the ascertainment of actuated keys by unauthorized tapping connections applied to the keyboard unit (12) or the cable (14).