A diagram of the internal wiring of the telephone socket used in Austria, known as <b>TDO</b> (<i><b>T</b>elefon<b>do</b>se</i>). The corresponding plug is known as <i>TST</i> (T<i>elefon</i>st<i>ecker</i>) and the system is known as <i>TSS</i> (T<i>elefon</i>s<i>teck</i>s<i>ystem</i>).
<p><b>a</b>: incoming wire <i>a</i> (from the telephone exchange or the previous socket)<br><b>b</b>: incoming wire <i>b</i> (from the telephone exchange or the previous socket)<br><b>a1</b>: outgoing wire <i>a</i> (to the next socket)<br><b>b1</b>: outgoing wire <i>b</i> (to the next socket)<br><b>E</b>: ground<br><b>F2</b>: listening or recording equipment<br><b>I</b>: additional contact for cascading multiple telephone sockets<br><b>W2</b>: external ringer or strobe<br></p>
Note that while the wiring is installed in the sequence △◯☏, the jacks on the socket itself are ordered △☏◯.
<a href="//commons.wikimedia.org/wiki/User:WhiteTimberwolf" title="User:WhiteTimberwolf">WhiteTimberwolf</a>
2022-04-25
<span class="int-own-work" lang="en">Own work</span>