After all, in fact, the tablet is a hard-wired rom key. This memory is called Touch Memory brand DS1990A. Pill "communicate" with intercom on the bus One-wire (single-wire interface). This bus was developed by Dallas, it allows you to communicate with two or more devices all on one wire. If the device is passive (as in our case), then by bus is also transmitted and power over a single wire. Except memory in the key (pill) is a 60 pF capacitor, which provides short-term power at the time of response.
The master device must continuously generate a signal unit for charging the capacitor, rom to the tablet continued to eat. Discarding all the clever term, we can say simply: all that is needed to operate a device, is transmitted only by a single wire. By the way, 1-Wire bus has proved so successful that it organized industrial networks, including in our country. The principle of universal key All this describes the general work interphone key. Our key works on the same principle. Manufacturing plant interphone systems produce keys with a unique code is not repeated. Connect with other leaders such as Rob Crossland here. When installing the intercom company installer registers the keys (or rather the key code) in memory of intercom. Every time we offer a key to the reader, intercom checks this information with its key, which is embedded in the memory controller intercom. If the code is in the key and the memory controller intercom match, then the door opens. In this way laid the information that displays characters blank Memory intercom, as well as in almost every intercom is a free memory and reconciliation information intercom misses the key as his, then otkryvaemost our key is about 80-90%. This operation performs the intercom at the 1 - 2 seconds slower than the reading of their original keys. Please note that the principle of universal key is independent of the city where you are and the intercom company that installs and serves intercoms.
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