Abstract: The present invention provides an antenna interlock system comprising an upper housing and a lower housing. The upper housing has first and second interlock tabs disposed along its interior wall, which correspond to third and fourth interlock tabs disposed along the interior wall of the lower housing, the interlock tabs each having an aperture shaped to closely receive the antenna unit. The interlock tabs are disposed relative to each other such that when the upper and lower housings are assembled together, the apertures in the interlock tabs together define a pathway for receiving the antenna unit, and such that when the antenna unit is inserted through the antenna opening and into the receiving apertures, the antenna unit and the interlock tabs hold the upper and lower housing together.

Abstract: An electronic tone ringer provides a distinctive ringing capability through the use of two oscillators which allow selection of four tones and four modulation rates. In determining the type of tone generated, formattable inputs select between frequency shift or amplitude modulation modes or disabling the modulation altogether to generate a single tone. In the frequency shift mode, two fundamental frequencies are generated which are related by a predetermined ratio, the output tone alternating between these two frequencies at one of four selectable modulation rates. In the amplitude modulation mode, a single frequency is switched on and off at the selected modulation rate. All of the tones are produced with a duty cycle appropriate for driving an electromagnetic acoustic transducer.

Abstract: In the disclosed coded telephone ringing signal method and circuitry, audibly distinguishable ringing codes are generated by alternately shifting between at least a pair of single frequency tones at different modulation rates. Other distinguishable ringing codes are generated by changing both the modulation rates and tone frequencies utilized.

Abstract: An electronic tone ringer responds to ringing signals on a telephone line while being unresponsive to dialing pulses or other signals on the line. Powered directly from the telephone line or alternatively from an external DC supply, the ringer uses a digital integration and detection arrangement for distinguishing between valid and invalid ringing signals. A distinctive ringing capability for the tone ringer is also available through the use of two oscillators which allow selection of four frequencies and four modulation rates.

Abstract: In an oscillatory signal generator circuit exceptional frequency stability is insured by the use of interrelated constant current sources (520, 521, 522) that provide an insensitivity to supply voltage variations over a wide range. Two of the current sources determine the duty cycle by controlling the charge and discharge current of a capacitor (C) in the circuit. A third current source determines the voltage swing on the capacitor. By varying the current output from the third current source, the generator circuit provides a variable frequency signal.

Abstract: An electronic tone ringer responds to ringing signals on a telephone line while being unresponsive to dialing pulses or other signals on the line. Powered directly from the telephone line the ringer uses current sources (223-226) to provide a high impedance to the ringer circuitry and an insensitivity to line voltage variations so that reliable operation of the ringer is maintained on long loops and with multiple ringers terminated on the line. A multitone signal for activating an electroacoustic transducer (300) is provided by frequency modulating a single oscillator (500) within the tone ringer.