Timing

Pulse interval and width are set with single-turn continuously variable controls from 5 ms to 5.5 s in three ranges. Pulse width is continuously variable from 50 µs to 550 ms in four ranges.

Modes of operation

In continuous mode, Isostim generates continuous square waves. In gated or external sync modes, externally applied pulses can generate trains or single events. Single pulses of finite duration can be produced using a push-button on the instrument's front panel. External/DC mode converts Isostim to a passive stimulus isolator.

Dual tone audible alarm

A tone sounds when an open circuit is detected or when system compliance is reached. A second tone, which sounds when a signal is applied to the input, can only be heard if the batteries have sufficient charge to operate the isolator. A violation light advises when pulse width exceeds the interval.

Current delivery

Stimulus currents up to 10 mA can be set on the front panel with a control knob and a two-position range switch. Output current is load-independent.

Power

Isostim model A320D is powered by readily obtainable 9-volt alkaline batteries (included). Under average use these will last several months before replacement is required. The rechargeable A320R is supplied with a nickel cadmium battery stack which provides 10-12 hours of operation before recharge is required. The A362 Battery Charger must be used with the A320R.