Reed sensors in Telephone Handsets
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 which use handsets and hook switches. 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 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.
Applications are classified as Position Sensing, Pulse Counting, Electromagnetic or Relay, Temperature Sensing or Magnet Biasing types. This application is classified as follows and the link gives more information on best practices to help select the most suitable AT band and matching magnet.
The Reed Switches and Sensors used in such applications need to be robust, durable and efficient in meeting a high life expectancy. Our engineers work hard in life testing our products under various conditions, and our intention is to ensure end product durability and life. Although we wouldn’t want to restrict any of our products for use in only certain applications, the recommended products for use in this application are listed below.
R5B Ultra-miniature Normally Closed SMD Reed Sensor
|Polarity Sensitive, Normally Closed (NC), 6.5mm body length. 5W switching capability at 0.35 A...Continue reading|
R2B, Normally Closed, SMD Reed Sensor
|Polarity Sensitive, Normally Closed (NC), 19.5 mm SMD and low-profile SMD pitch. 10W switching...Continue reading|