Models 181T and TR are general purpose, variable persistence storage oscilloscope mainframes with plug-in capability. The instruments, as shipped from the factory, are intended for bench use. The Model 181TR can be rack mounted as described in Section II. The storage feature can be used to store singleshot occurrences for later viewing or photographing. Comparison of waveforms can be accomplished by storing several separate occurrences and later viewing them simultaneously. The horizontal amplifier has a direct-coupled bandwidth of dc to 5 MHz. The ac-coupled bandwidth is 5 Hz to 5 MHz with a dynamic range of ±20 volts. The amplifier has front-panel selectable deflection factor ranges of 1 V/div (XI), 0.2 V/div (X5) and 0.1 V/div (X10). A vernier control provides continuous adjustment between ranges. A front-panel BNC connector permits the use of external deflection signals. The external input impedance is 1 megohm shunted by approximately 30 pF.