| 摘要 |
A multiplexed dual tone multi-frequency (DTMF) encoding/decoding system for remote control applications is provided whereby simultaneous combinations of activated switches may control a device at a remote location via a conventional DTMF encoder/decoder system. The system utilizes a unique multiplex type DTMF signaling technique to increase the previously possible number of coded signals generated and correspondingly decoded. Each desired combination of activated switches results in the activation, by a first read only memory and an oscillator-divider, of a pair of data lines which in turn activate a DTMF tone encoder, resulting in the generation of a pair of dual tones in alternating sequence which are transmitted over a single channel communications link to a DTMF decoder. The decoder converts each dual tone signal to a code, activating a desired pair of data lines. A pulse stretcher then holds the activated state corresponding to one of pair of activated data lines while a second dual tone signal is received and converted to a code, activating an additional desired pair of data lines. A third read only memory receives the four signals corresponding to the pair of encoded dual tone signals and activates a desired combination of relays or other control devices. A filter/momentary hold array may be added between the third read only memory and the control device to eliminate extraneous signals and to provide a smooth transistion between changes in combinations of activated switches.
|
