As you know, the greater the number of elements in the design, so it is less reliable. To increase the reliability of electronic devices and selection circuitry. This will be the conversation below.
For several years the authors have used to protect separately stasey unheated garage guard device for industrial production with a sensor, which was normally closed contacts. The design of the sensor used a steel ball and spring-loaded contacts, and the sensor, despite regular sealing gasket, not even in extreme cold refused to work. The very same watchdog had a minimum of parts, and therefore never fail. Its simplified schematic diagram is shown in Fig.1. When breakage of the line or its short circuit relay disconnected and rang the bell. It was therefore decided to replace the device this sensor is on the other with normally open contacts (see Fig.1, 2 and photo). During the winter of last year there was not a single rejection watchdog the device even in quite severe frosts.
It would be unwise, having a two-wire line to the garage for the guard device not to fail there and network voltage. After all, lighting inside the garage, charge the battery, plug in a circular saw or grinder — all this can be done only from the network That was implemented In Fig.S shows a diagram of a guard device elements of the switching sensor and is interlocked with it’s line of household lighting SEG voltage of 220 V.