Abstract: A circuit that combines the functions of audio compression and voice detection comprises an amplifier in a negative-feedback configuration in which the feedback signal is the product of the output of the amplifier and a syllabic voltage derived from that output. The syllabic voltage is compared with a threshold level to provide an output that is a measure of the presence of a voice signal. In an alternate embodiment, the syllabic voltage is compared with the sum of a threshold level and a detected syllabic voltage to generate a signal that is a measure of the presence of voice. The syllabic detector may be either an averaging detector or a valley detector.

Abstract: Circuitry for synthesizing a busy or reorder tone comprised of a first tone having a frequency of 770 Hz and a second tone having a frequency of 1150 Hz is described. The inventive synthesizing circuitry requires only one clock oscillator, whose output is coupled to a programmable divider. The programmable divider is switched between two divisor numbers at a frequency that is substantially one-half of a frequency selected from a predetermined range of frequencies substantially midway between 770 Hz and 1150 Hz. In the preferred embodiment, the programmable divider output is switched between frequencies of 1250 Hz and 883.3 Hz at a 500 Hz rate. The programmable divider output is then interrupted at a 2 Hz rate to provide the synthesized busy signal. The inventive synthesizing circuitry may be advantageously utilized in mobile or portable radios for providing a busy signal that sounds essentially identical to a fast busy or reorder tone comprised of two tones.

Abstract: A releasable, hook-type fastener of the kind intended to secure pieces of equipment or structural members together, the fastener including a casing, a drive shaft turnable in the casing, an eccentric bushing carried by the casing and turnable with the shaft, and a pair of separate and distinct, similarly-shaped spring hooks that are disposed side by side and substantially in broadside contact with each other. At one end, the hooks have looped bearing portions which are frictionally engaged with the eccentric bushing, and at the other end they have registered bill portions. A pin is provided, separate from the hooks and adjacent to the eccentric bushing, for engagement with the hooks so as to maintain them in registration with one another. The arrangement is such that an unusually strong and sturdy construction results, without the need for heavy gauge springs and without the use of odd-shaped springs which would require special metal stock and bending fixtures or jigs for their fabrication.