The NL800A is a battery powered, opto-coupled isolator (replacing the NL800), which has been designed for low noise applications such as in vitro and in vivo electrophysiology. It has a constant current output, with very high output impedance, making it suitable for stimulation through microelectrodes as well as with gross electrodes. Normally driven from the NL510A or NL512 buffer modules, its output current is either set by the 10-turn control on the NL510A, within the output range set by the switch on the NL800A or by the amplitude of the voltage waveform applied to the NL512 (or directly to the NL800A). Output pulses have the same timing as the input pulses (2 micro-seconds to 30 seconds output pulse width). The NL800A is supplied with a set of 5 GP23A batteries, a pair of 1mm output plugs and heat shrink sleeving.