Used with Holter recorders to observe real-time ECG waves on computer monitor. Specifications: Input Port: Phone Jack Output Port: USB Insulation Voltage: 4000V ACFeatures: Used with Holter recorders to observe real-time ECG waves on computer monitor, applicable models are DMS300-2, 300-3, 300-3A, 300-4, 300-4AMGY-H3, MGY-H3M, MGY-H4 and MGY-H4M. Holter Insulation Cable