Continuous Tone-Coded Squelch System

Abstract: The utility model relates to a digital interphone with a digital and analog hybrid receiving function. A receiving circuit is composed of a voice encoding and decoding chip and a digital interphone baseband signal processing chip SCT 3252. By means of Continuous Tone Coded Squelch System/Continuous Digital Controlled Squelch System (CTCSS / CDCSS) technology, identification of a digital call and an analog call can be realized. In a decoding stage, in the first 20 ms, analog demodulation is performed on codes, and extraction of a CTCSS code is performed on the codes. If a CTCSS code is not extracted, digital demodulation is performed on the code, and the digital interphone is converted into a digital receiving state; and if a CTCSS code is extracted, and the CTCSS code is consistent with a CTCSS code that is set by the digital interphone, the digital interphone is converted into an analog receiving state. As a result, the digital and analog hybrid receiving function can be realized. The digital interphone with the digital and analog hybrid receiving function of the utility model capable of improving a frequency spectrum utilization rate provides a solution for frequency crowding; and further, the digital interphone is of long-term significance.

Abstract: A squelch tail eliminator for use in a receiver having a continuous tone coded squelch system and provision for the disabling of the tone coded squelch system is disclosed. A pulse generator, responsive to the discontinuance of a given tone, generates a gating pulse that inhibits the disabling of the tone coded squelch system for the time duration of that pulse, providing squelch tail elimination at the end of a message transmission indicated by the discontinuance of the tone.

Abstract: A retrofit energization arrangement especially suitable for an aircraft wherein original factory-placed wiring can be reused in common bus form for plural new loads in order to avoid the expense and hazard of disassembling original wiring bundles for new conductor incorporation. Serviceable wiring possibly earlier retired in place or becoming unneeded from equipment removal can, by way of the invention, be used for plural diverse new loads including loads of disparate operating cycle and current requirements for example, even though energized via a common bus. In the disclosed apparatus both energizing current and load control signals are transmitted via the same electrical bus between control location and load areas of the aircraft where control decoding and energy tap-off occur, the latter by switch mode power supply if needed. Control signals of sinusoidal waveform, minimal electromagnetic and radio frequency interference character and limited existing bus filtering attenuation are disclosed; these may be embodied as the Frequency Shift Keying (FSK) or Continuous Tone Coded Squelch System, CTCSS, frequencies used in the radio communication art. Loads of differing types are disclosed as examples in the described embodiment of the invention; additional loads are feasible. Use of the invention in land vehicles, watercraft and building structures is also contemplated.

Abstract: A switched microphone hang-up bracket includes an outer case for receiving a microphone which is releasably secured thereto. The microphone is of the type which may be used in a mobile two-way radio system having a continuous tone coded squelch system (CTCSS) disable switch. The bracket includes a camming device for mechanically placing the switch in either the enable or disable mode to selectively place the receiver in a "noise squelch" and "channel monitoring" mode or in the off position, as desired, while the microphone is in place in its bracket.