Patent GB-1166283-A (GB)
Title: Telephone Extension System with at Least One Remote Extension Station.
IPC: H04M1/72505
Filed: 1966-10-07
Abstract: 1,166,283. Exchange systems, sets, mouthpieces; radio signalling. CHROMALLOY AMERICAN CORP. 7 Oct., 1966 [23 Oct., 1965], No. 45030/66. Headings H4J, H4K and H4L. A transceiver for remote control of a subscriber's telephone at a fixed base station, transmits on a carrier frequency continuously modulated with a coded component and the base station incorporates a hang-up signal detector responsive when both the coded component and voice signals are absent. The base station responds only if the coded component is present and thus reduces the risk of false operation. When not in use the transceiver 4 is placed in a battery charger 5 and the handset of the telephone at the base station 3 is replaced on the cradle and is used in the normal way. To condition the base station for remote operation the handset is removed and positioned so that its mouthpiece and earpiece are located in microphone and speaker receptacles 7 and 6 respectively. The handset depresses a button 8 causing a T-shaped lever 200 to depress the cradle switch buttons. The mouthpiece and microphone are coupled by an acoustic coupler 203 comprising two portions 90, 91 which sealingly engage the rims of the microphone and mouthpiece to form two cavities 92, 94 connected through a constriction 97. The base station incorporates a transceiver which is normally set to its transmit mode and responds to the ringing tone of an incoming call to transmit the ringing tone to the transceiver 4. When the subscriber responds by pressing the push-to-speak button 9 his transceiver commences to transmit the coded component which is a continuous tone beyond the voice frequency range. The base transceiver responds to the receipt of this tone by energizing a solenoid causing the lever 200 to pivot upwardly releasing the cradle switch and completing the connection. If the transceiver 4 is not provided with means to initiate a call an interlock circuit at the base station may be switched in and is arranged to prevent a coded signal received in response to inadvertently pushing the button from releasing the cradle switch unless incoming ringing tones are present. Alternatively the transceiver may be provided with a dial arranged to effect a slight shift in the code tone. The base station responds by operating a dialling contact thus sending the appropriate dialling pulses to line. At the end of the conversation a circuit responds to a predetermined lapse of time after the last receipt of voice signals or the tone code, and hangs up the handset at the base station by releasing the solenoid so that the lever 200 again depresses the cradle-switch buttons. A circuit which releases the solenoid in response to the detection of the distant party hanging up his handset is also included. Mobile transceiver.-In the mobile transceiver (Fig. 4) the crystal controlled oscillator 320 used in the transmitter section to generate the carrier is routed to the receiver 310 via a switch 302 during the receive mode and used as the heterodyning signal, and a single transducer 306 is used as a microphone-loudspeaker. The transceiver is normally in the receive mode in which signals from the antenna 300 are routed through the receiver 310 and thence via an audio amplifier 305 to the transducer 306. When the mobile subscriber answers by operating a push-to-talk button, switches 301 to 304 change over to the transmit mode and route signals from the transducer via a compressor to the audio amplifier and thence via the switch 303, where they are combined with the tone from the encoder 307, to the transmitter section and thence to the antenna 300.