Quartz time switch week 1 changeover contact 230V/50-60Hz 3TE auto. SO/WI changeover Mechanical time switch SENTRON 7LF5 for the time-controlled switching of electrical consumers, e.g. lighting or industrial control systems. The mechanical time switches from Siemens are particularly robust. The 7LF5 time switches are available as synchronous or quartz time switches for DIN rail or wall mounting with different time ranges and with different auxiliary contacts. 7LF time switches - safety, comfort and energy saving.