TEF4S-ON is a frontal electronic timer used to realize the timing function and allow a compact solution in the cabinet compared to separate timers. TEF4S electronic timers, equipped with spring terminals, are front-mounted and locked on AF, AFC contactors or NF, NFC contactor relays equipped with screw or push-in terminals. A mechanical indicator allows to show the state of the contactor. TEF4S electronic timers are supplied by a direct plug-in parallel connection to the coil terminals A1 - A2 of the contactor or contactor relay. A varistor is integrated on the timer to offer a built-in protection against surges in the contactor coil. The TEF4S is available for a wide control voltage range 24...240 V AC/DC. TEF4S allow time-delayed functions up to 100 s in 3 distinct time ranges, independently of the control system. The time delay ranges are selected by a switch and the time delay can be adjusted by means of a rotary switch. The timing function of TEF4S-ON is activated by closing the device on which the timer is mounted.