The base for this circuit came from a proposal from around 1970 for a Morse Writer – if the speed was too high or you had no pencil and paper to write down the heard sequence. The schematic included an automatic start and stop of the transportmotor for the papertape. My until now not complete mechanical working prototype (not enough time…) looks like this:

    Please have a closer look at the top of the plotter pen: a simple relay (with removed contacts) presses down the pen and so the dots and/or dashes will be seen on the paper tape. On the photo the pen has still his plastic cap. After removing that cap the pen mechanicsm can be turned in an upright position and is ready for start…

    May be you receive following signal:   . _ . .     .     _ . _ .     _     . _ .      _ _ _     _ .  (what does it mean?)

    The input is a portable radio via a plug for headphones, volume control of the radio in mid position and up it goes!

    Here is a photo of the Greger construction with a similar relay, prepared for this action. To the left three different views of the same relay (5 V, 50 Ω). On the switching middle contact (=anchor) is soldered a short wire connected with the chin. Lips and “throat” (folded for the open/close action) are made from onesided red colored craft cardboard.

    The front view of this special block:


    …and the complete circuit:


    Please note the original Egger Lectron groundplate (blue frame, quality like a mirror!) from 1966.

    My first tries: using the Egger microphone block (like shown in GB patent 1,217,885 from 1967) with a 2-stage pre-amplifier and power output (LM386)  – but the total amplification was not high enough or resulted in oscillations… So I decided to go the proven way with headphone plug ( and to hear – and for video recording – parallel my on cassette recorded text with a serial 16Ω speaker module).

    I had to use a power supply, because the consumption with up t0 0.25 A and stable voltage is not possible with batteries. I had success with volume control (radio recorder as input) and voltage regulator between 6.5 and 8.5 V.




    • This reply was modified 3 years, 2 months ago by Guenther.
    • This reply was modified 3 years, 2 months ago by Guenther.
    • This reply was modified 3 years, 2 months ago by Guenther.