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A  Closer  Look  ...

» HOW THE TELEPHONE DIAL SYSTEM WORKS «

...  to  prevent  contacting  users  while  SSW  Relais  is  in  motion.

The  DIALER'S  PULSE-TIMING  shown  ...
( Diagram  glued  on  its  Back  Side )

THE  DIAGRAM  OF  THE  REVISED  DIAL  SYSTEM  ...

THE  BUILDING  BLOCKS  ( with  the  Diagrams  on  its  Back  Sides )  ...

 ``` H O W T H E E X P E R I M E N T A L D I A L S Y S T E M W O R K S : ***************************************************************************** RELAIS (RELAYS) and their associated CONTACTS are shown in the SAME COLOR. where: r = "rest" Contact is closed when the relais is not activated. a = "active" Contact is closed when the relais is activated. SSW(r12) opens, when the SSW ( = "Schritt-Schalt-Werk" ) reaches POSITION 12. SSW(r02) opens, when the SSW ( = "Step-Switch-Work" ) is in motion. SSW(r01) ( with RR(r) & DR(a), the ACTIVE TIME DELAY of DR-Relais ) ensure that NO USER CONTACT is made when the SSW is in motion. The DIAGRAM shows an IDLE STATE with USER "3" SELECTED. To change the user, first a RESET is necessary. Pressing ( and releasing ) the RESET Button activates the RESET-Relais, because SSW(r12) is closed. With RR(a1) it holds its own activation and with RR(a2) it starts the PULSAR-Relais. The PULSAR- Relais activates with PR(a) the SSW until the SSW reaches position 12 and opens SSW(r12). This deactivates the RESET Relais and opens RR(a1) & RR(a2). This stops the PULSAR Relais. The RESET Position is found. Selecting (e.g.) a new USER "6" by DIALING the "6" lets the SSW move 6 steps to position "6". After a DELAY TIME contact DR(a) connects the USER "6" ... R E M A R K (DR) DELAY-RELAIS: S1 = T1 = ON-Delay; ( S2 = T2 = OFF-Delay ) See ... "HOW THE PULSAR IS WORKING" ... in the chapter COUNTERS. Back to the Photo with the Building Blocks ... IN A REAL R E L A Y D I A L S Y S T E M from 1950 (eg. DEUTSCHE POST) "SSW"s were connected in a tree-like structure. When customer A picks up his hand set, the 1st SSW connects customer A with the (FERNMELDEAMT in German) SWITCHING STATION and customer A gets a DIAL TONE. When customer A dials, every digit activates a SSW in sequence until the selected customer B is contacted. Pulses from the SWITCHING STATION activates the RINGER in B's station. Customer B picks up his hand set and the connection between A and B is established. When the conversation is finished, A and B hang up and all SSWs are RESET ... Have a look at the DEMO-VERSION of a 4x12-Step-SSW ... The SSW 0/12 Position-Control-Plugs LEFT ... RIGHT the SSW Power-Plugs Historical Remarks ... impressum: ***************************************************************************** © C.HAMANN http://public.beuth-hochschule.de/~hamann 09/10/11 ```