Even though the telephone was ubiquitous in the 80s and 90s even every home or office, it has been replaced with cellular phones or smart phones. Offices though, still continue to use desktop telephones. This makes it easier for higher level management to get connected on external calls by their secretaries or receptionists as well as internally, via an intercom system, to a PBX or a private branch exchange. These telephone appliances, make many of calls a day and the handset is placed back on the base station when hanging up a call. To avoid static when using mechanical switches in the base station, handset designers use normally closed reed sensors on the base station, with a magnet on the handset. This also helps remove the noise of the handset being placed on the base station and the user at the other end always gets a silent ending to a call. When the handset is taken off the base station, it closes the normally closed reed sensor and enables dialing circuit. In the case of wireless handsets, the same sensor is also used to trigger the charging circuits.
