Specification :

The MLS-4B is a stable, precise and portable instrument for field and laboratory use, it works not only at 1310/1490/1550nm (recommended by ITU-T, for PONs), but also 650nm for locating breaks within OTDR dead zones.
Two optical ports, 4-wavelength selectable
Adjustable output power
LCD with back light for operation in dark environment
Modulation frequencies 270Hz,1KHz, 2KHz, 2Hz (@650nm)
Automatic wavelength recognition
Two-way powering system: AC adapter and rechargeable batteries
Battery capacity indicator with auto-off function