HP 44425A is a 16-channel, isolated, digital input/interrupt assembly. It can be used with HP-3497A Data Acquisition/Control Unit and/or HP-3498A Extender, providing optically isolated input channels, 8 of which can be sensed for interrupt purposes. It features optically isolated handshaking to synchronize data transfer between a peripheral and the HP-3497A. Additionally, manual changes necessitated by circuit board revision or errata in documentation are provided in a Manual Changes Supplement, which can be periodically requested.