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Mieco 25 A
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Mieco 25A
Code Phone Scrambler

Mieco 25 and 25A were analogue scrambler phones produced by Mieco (USA), a subsidary of Polarad Electronics Corporation (USA) in the 1970s. The phone uses a simple frequency inversion scheme (commonly known as a scrambler) with 25 settings, and was interfaced to a standard telephone set by means of an acoustic coupler. It was sold well into the 1980s.

The image on the right shows a typical Mieco model 25A in action. It consists of a handset, an acoustic coupler and some controls, housed in a rectangular metal case. The device is operated from either a 4.2V or 9V battery, and two dials with 5 settings each are used to set any of 25 possible 'codes'.

The handset of a regular telephone set is placed on the acoustic coupler inside the Mieco 25. The difference between model 25 and 25A, is that the acoustic coupler of the latter is adjustable to accomodate phone handsets of different sizes.
Operating the handset of the Mieco 25A

The initial version of the Mieco 25, was powered by a TR-133 Mallory 4.2V battery. Later versions with a serial number of 4584 or higher, such as the one shown here, used a standard 9V block battery, such as the Eveready 522.