Intercom equipment development history

The intercom equipment was first produced in the 1920s and was born in the laboratory of Westinghouse. An ingenious inventor named John Kermode wanted to automate the sorting of postal documents. At that time, every idea of ​​the application of electronic technology was very novel. His idea is to make a walkie-talkie mark on the envelope. The information in the walkie-talkie is the address of the addressee, just like today's postal code. For this reason, Kermode invented the earliest walkie-talkie logo. The design scheme is very simple, that is, one "bar" indicates the number "1", and two "bars" indicate the number "2", and so on. Then, he invented a walkie-talkie reading device consisting of basic components: a method capable of emitting light and receiving reflected light to measure the reflected signal strip and space, that is, an edge positioning coil; and a method of using the measurement result, namely, translation Code.

Kermode used the newly invented photocell to collect reflected light. The "empty" reflects back a strong signal, and the "bar" reflects back a weak signal. Unlike today's high-speed electronic component applications, Kermode uses magnetic coils to measure "strips" and "empty". Just like a child connecting a wire to a battery and wrapping it around a nail to hold the paper. Kermode uses a coil with a core to attract a switch when it receives an "empty" signal. When it receives a "strip" signal, it releases the switch and turns the circuit on. Therefore, the earliest walkie-talkie readers were very noisy. The switch is controlled by a series of relays, "on" and "off" depending on the number of "bars" printed on the envelope. In this way, the walkie-talkie symbol directly sorts the letter.

Shortly thereafter, Kermode's collaborator Douglas Young made some improvements based on the Kermode code. The amount of information contained in the Kermode code is quite low, and it is difficult to compile more than ten different codes. The Young code uses fewer bars, but uses the size change between the bars, just like today's UPC walkie-talkie symbols use four different strip sizes. The new walkie-talkie symbol encodes one hundred different regions in the same size space, while the Kermode code can only encode ten different regions.

Motorola GP328 walkie-talkie appearance collection

It was not until the 1949 patent document that the first comprehensive walkie-talkie symbol invented by Norm Woodland and Bernard Silver was recorded. In the previous patent literature, there was no record of walkie-talkie technology, and there was no precedent for practical application. The idea of ​​Norm Woodland and Bemard Silver is to use Kermode and YOung's vertical "strips" and "empty" and bend them into a ring, much like an archery target. In this way, by scanning the center of the graphic, the walkie-talkie symbol can be decoded regardless of the orientation of the walkie-talkie symbol direction.

In the process of continually improving it with this patented technology, a science fiction writer Isaac-Azimov describes in his book "The Naked Sun" a new way of using information coding to achieve automatic recognition. At that time, people thought that the walkie-talkie symbol in this book looked like a square checkerboard, but today's walkie-talkie professionals will immediately realize that this is a two-dimensional matrix walkie-talkie symbol. Although this walkie-talkie symbol has no orientation, positioning, and timing, it is clearly represented by a high information density digital encoding.

It was not until 1970 that Iterface Mechanisms developed the "two-dimensional code" that there was a printing and reading device for a two-dimensional matrix walkie-talkie that was suitable for sale. At that time, the two-dimensional matrix walkie-talkie was used to automate the newspaper typesetting process. The two-dimensional matrix walkie-talkie is printed on a paper tape and scanned by today's one-dimensional CCD scanner. The illumination from the CCD is on the tape, and each photocell is aligned with a different area of ​​the tape. Each photocell outputs a different pattern according to the printed walkie-talkie on the tape, and combines to produce a high-density information pattern. In this way, a single character can be printed on the same size space as a single strip in the early Kermode code. Timing information is also included, so the whole process is reasonable. When the first system entered the market, the full set of equipment, including printing and reading equipment, cost about $5,000.

Shortly thereafter, with the continuous development of LEDs (light-emitting diodes), microprocessors and laser diodes, the new logo (symbolism) and the explosion of its application were ushered in what people called the "interphone industry". It is rare today to find companies or individuals who have no direct contact with the fast and accurate walkie-talkie technology. As the technological advancement and development in this field is very rapid, and more and more application fields are being developed every day, it will not take long for the walkie-talkie to become as popular as light bulbs and semiconductor radios, which will make each of us live. It has become easier and more convenient.