The TKN-3P viewing unit is a binocular periscopic telescope for tank or armoured carrier commander, designed for working at day-time as well as at night-time. For night-time work the unit is provided with a channel image intensifier of 2+ generation, working in passive mode without additional lighting. Only residual illumination of the night sky is taken advantage of. The day-time branch has a scale for range finding. For operation in winter the unit is equipped with eyepiece heater. Without any modification the TKN-3P can substitute the active units TKN-3 used hitherto.