No. B004
Noise switch ---Telephone-two-call device---
This acoustic switch works with a microphone and a relay. Whenever there will be any kind of noise (e.g. ringing of a telephone, doorbell etc.), the relay will switch on, and if the noise stops, the relay will switch off. With the aid of this device you may activate in other rooms bells, lamps, etc. Ideal for persons with hearing problems, for rooms with high ambient noise levels, as acoustic alarm system etc. The pick-up sensitivity is adjustable. Operating voltage is 9 Volt.
	The microphone capsule should not be soldered directly on the printed circuit board, because otherwise the rattling of the relay would be transferred acoustically to the microphone and lead to a constant pick-up of the relay. It is convenient to connect the microphone with the printed circuit board using short, soft litze of max. 8cm, and in case of fitting it in a box, it should be well padded (foam rubber). Please consider the correct polarity of the microphone (at the parts diagram it is seen from the underside). The printed circuit board needs an operating voltage of 9V, current load max. 120mA. The current supply must be sufficiently strong (car accumulator) because otherwise the device will not operate correctly (relay may rattle). With too long and too thin current leads it may happen, that the operating voltage during the pick-up of the relay does not stay constant enough, and as a result of the voltage variation the relay may be picked up in rhythm. For that purpose it is necessary to connect parallel to the current supply input directly on the printed circuit board an elca of 1000µF 16V (not included in the construction set). Through the trimmer sensitivity is adjustable. The board should always be fixed close by the noise generator (telephone, doorbell) and the sensitivity be adjusted as low as possible. The device will, then, react less on strange noises and be only activated if the desired bell or telephone rings.
	Tin-plated board! Fitting case: KEMO G027 Board dimensions: approx 55 x 45mm Price group: 6