Devised, researched
 and written
  Peter King Smith BSc

                                                         The mid-1960s, German-built multi-track tape recorder with FM/AM/SW radio

2nd Main Patent

Patent no.: CH432039 

Tape recorder with multiple soundtracks

Key facts:

  • Drawn up in German 
  • Applied to: Federal Office for Intellectual Property (IGE), Bern, Switzerland 
  • Applicant:  Standard Telephon und Radio AG, Zurich 
  • Applied:     17 July 1964 
  • Granted:    15 March 1967 
  • Includes:   3 earlier patent applications ("priority claims"for key Music Center inventions  
  • Includes:   4 diagrams, all of which had been originally registered with the DPA in Munich 

Priority claims

The following table shows three earlier patents (aka 'priority claims') that were annexed to this second main patent, and submitted by Standard Telephon und Radio AG submitted to the Federal Office for Intellectual Property in Bern, Switzerland on 17 July 1964.

No. Patent No. Earlier Patent (priority no.) Registered on Title of Invention Inventors
1 DExxxxxx 20883 IX Not known Untraced Not known
2 DE1177841 20884 IX 20-7-1963 Circuit arrangement for interrupting playback or stopping the sound carriers in tape recorders Friedrich Knochenauer Siegfried Apitz
3 DExxxxxx 20885 IX Not known Untraced Not known

Two out of the three priority claims could not be traced. The nature of the other inventions can nevertheless be identified from the figure descriptions in the drawings that were submitted with the second main patent.

The inventions
On the basis of the three priority claims, the development team's key inventions were: 
  1. A wide magnetic tape with multiple, parallel recording tracks. 
  2. A device for generating and storing a pilot signal on a wide tape. 
  3. A device for detecting a pilot signal on a recording medium. 
  4. A device for stopping sound reproduction (playback).  
It is possible that there was a fourth priority claim as there are four inventions, but this has not been found.

Patent claims

The following claims were made in this patent application:
  1. A magnetic tape recorder with multiple tracks. 
  2. A device for automatically recording pilot signals onto a tape, in order to mark the end of a recorded track. 
  3. Device automatically detects a 'stop-playback' marker recorded on the tape. 
  4. At the end of a track, a circuit arrangement stops sound reproduction, whereupon a pilot signal is generated, causing: 
    • The sound head to move away from the tape 
    • The tape transport to stop, after the pilot signal has been recorded.
      [tape rewind is then initiated] 

The inventors
The second main patent application CH432039 for this tape recorder recognises two co-inventors from Altena, Westphalia, Germany:
  • Friedrich Knochenhauer 
  • Siegfried Apitz 


The second main patent application was submitted by Standard Telephon und Radio AG of Zurich.


The following 4 diagrams (3 electrical; 1 material) shown below were submitted together with patent application No. CH432039. The drawings, which have been grouped, will have been exactly the same as the individual ones submitted with the earlier three antecedent patent applications. 

Fig 1: Wide magnetic recording tape showing:
- Multiple, parallel soundtracks (1-6)
- Location on the tape where magnetic recording begins on all tracks (8)
- Transparent section on recording tape (9) used to detect the beginning of the recordable tape
and to initiate a rewind stop.

Fig 4: Means for automatically stopping sound reproduction.

Fig 2: Circuit arrangement for detecting a pilot signal on a recording medium [ed. tape].
Fig 3: Circuit arrangement for automatically stopping sound reproduction in tape recorders (20884).

1. It is clear from the above claim that the inventions of pilot-signal generating and detection devices were key components that had been left out of the first main patent, as there is no mention of such devices either in the first main patent or its antecedents (aka: priority claims).

2. The function of the pilot signal (when heard: a pilot 'tone') is to mark the point at which sound reproduction (playback) should stop. The invention uses a basic circuit to store a signal on the recording medium and then detects that signal later when a recording is replayed. The detected pilot signal will then activate a mechanism which stops further playback and initiates a tape rewind.

© Researched, translated and adapted by Peter K. Smith, 26 June 2008