Keypad
A key pad ( TWB ), and dial pad , the assembly of a touch-tone telephone from the 1970s - 90s, with the want to call number is dialed. In later telephones, the keyboard is usually integrated into the circuit board.
technology
The use of keypad to dial the digits of phone numbers became widespread in Germany in the mid- 1970s . Advances in microelectronics made it possible to manufacture numeric keypads inexpensively. The keypad replaced the mechanical number switch . In contrast to this, in addition to the classic pulse dialing method (IWV), the diode-earth method (DEV) and the multi-frequency dialing method (DTMF) and convenience functions, such as redialing, could be implemented with the keypad . The electronics were integrated on a circuit board in the TWB. The interface to the telephone electronics was standardized, the different TWB variants were interchangeable.
The keypad consists of keys with the digits 1to 9and the 0, which are essential for dialing numbers , as well as additional keys with special functions, such as the *and #key for controlling performance features and telephone system functions .
In addition to the model shown here with one switching contact per key, on which the short keys can be pressed softly without resistance, there was also a more "mechanical" keypad, in which the keys protrude 6 millimeters from their base and when pressed, a noticeable and have an audible pressure point (e.g. on the Siemens FeTAp 755-1 telephone). Here each key operates a slider for row and column, which in turn act on their associated switches.
Type designations
| Type designation | Electoral process |
|---|---|
| TWB 71 | Multi-frequency dialing (DTMF) |
| TWB 73 | Diode-earth method (DEV) |
| TWB 75 | Pulse dialing (IWV) |
| TWB 78 | DTMF, 16 keys with special keys A, B, C and D for operating procedures (e.g. for GEDAN ) |
| TWB 80 | optional DTMF or IWV, 16 keys with special keys A, B, C and D for operating procedures (e.g. for GEDAN), special keys only with DTMF |
development
Keypad blocks were mainly used in the FeTAp telephones of the Deutsche Bundespost and contemporary telephones in other countries. Later devices of the Bundespost (e.g. Tel 01 LX ) still had the same keyboard appearance, but the keyboard was only a switch matrix and connected to the electronic circuit board via a conductor foil . All electronics for generating the dialing signal could now be found there.
literature
- Lothar Wilhelmy: The new postal keypad for the impulse dialing process , electronics, Franzis-Verlag Munich, 1977, issue 12
- Werner Bärwald: Expert practice lexicon communication technologies. Networks - Services - Applications . Expert Verlag, Renningen 2009, ISBN 978-3-8169-2843-0
- Dietrich Arbenz From drum voter to optiset E - The history of wired telephones for Siemens' private branch exchanges (1950–2000) , Herbert Utz Verlag, Munich 2009, ISBN 978-3-8316-0908-6
- Peter R. Gerke: Digital communication networks . Springer Verlag, Berlin / Heidelberg 1991, ISBN 978-3-642-93459-9
See also
Web links
- The telecommunications network in Germany (accessed on August 21, 2017)
- The telephone, its networks and their influence on everyday private life (accessed on August 21, 2017)
- How does the connection come about? (accessed on August 21, 2017)