Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Transfer Contact for Small Signal Applications

IP.com Disclosure Number: IPCOM000091260D
Original Publication Date: 1967-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Humphrey, DG: AUTHOR [+2]

Abstract

The tuned circuit is particularly suitable for use in touch tone dialing systems and similar devices. This is because it provides a rest tone without complicating the circuits.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Transfer Contact for Small Signal Applications

The tuned circuit is particularly suitable for use in touch tone dialing systems and similar devices. This is because it provides a rest tone without complicating the circuits.

The tuned circuit includes capacitor C, inductor L, and diode D. Each tap on L is connected to one of N switching circuits SW. The latter connect the associated tap to ground reference potential when the switching circuit is selected. When all switches S are open, diode D is forward biased by +V through resistor R2. Since no base current flows in transistors T, the collector- emitter junctions of the transistors have a very high impedance. Under these conditions, the resonant frequency of the tuned circuit is inversely proportional to the square root of L, the total inductance in the circuit.

When one switch S such as is in SW1 is closed, the associated transistor T is forward biased since base current is established through resistor R1. The collector and emitter junctions of transistor T provides a low impedance path between the associated tap and ground. Under these conditions, diode D appears as an open circuit and the resonant frequency of the tuned circuit is inversely proportional to the square root of L2. The value of L2 is determined by which switch of the N switches is closed and the placement of the taps on L.

1

Page 2 of 2

2

[This page contains 2 pictures or other non-text objects]