The SB/STuZH timeswitch is a synchronous motor driven timer, which has been specifically designed to be fitted in place of a three-pin 13 amp socket outlet. The socket outlet can be removed and disconnected from its back box, or patress, and the socket box timeswitch is fitted in its place. Any device rated at not more than 16 amps resistive, can then be permanently wired via the socket box timer, and controlled by the dial with captive tappets.

This is another unit which makes use of the familiar Grasslin FM/1 synchronous timeswitch module. The product therefore has the normal features associated with this module - 96 captive tappets switching for a fixed period of 15 minutes per tappet. All tappets between the ON and OFF times must be moved to the outer edge of the dial. A three position manual override is built in to the dial of the timeswitch, giving Timed, Fixed on, and Fixed off control. The unit features clock hands so that it is easy to set the dial accurately (and to read the current time from the dial). There is a seven day version of this timeswitch, the SB/SWuZH - the dial of this unit is divided into seven sectors, corresponding to the days of the week. Each captive tappet within the seven day dial switches for a fixed minimum period of two hours.

A popular application for this unit is controlling fixed lighting. As has been stated before, caution must be excercised when connecting to a lighting load. Conventional ‘light bulbs’ (tungsten lighting), will draw an ‘inrush’ current of approximately 10 times the running current. On this basis, the maximum safe tungsten lighting load is approximately 350 watts. Other types of lighting are worse in terms of inrush current. Fluorescent lighting will draw an inrush current of approximately 15 times the running current (i.e max. fluorescent load 250 watts). Fluorescent lighting with ‘power factor correction’, and discharge lamps (often referred to as "SON" lamps) are even worse! Technical advice should be sought before connecting to this type of load. The inevitable result of connecting any timeswitch to a load which imposes too much electrical stress on the contacts, is that the timer cannot switch off, because the switch contacts have been welded together. It is often the case that fluorescent and discharge lighting is thought of as an ‘inductive’ load by installers, therefore they refer to the inductive rating which we publish, and assume that everything is o.k.. Unfortunately, this is an error. These types of loads are not simply inductive, but are much more complex. The subject is a complicated one, which this document does not attempt to cover in detail, but these notes should suffice as guidelines to excercise caution.

Another popular application is to control an immersion heater with a socket box timeswitch. The unit is electrically capable of controlling this type of load, but has not been designed with this in mind.