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Electronic Subscriber Set With Improved Flashing

IP.com Disclosure Number: IPCOM000048213D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Diehl, V: AUTHOR [+2]

Abstract

The figure is a schematic of the circuit for a telephone subscriber set using a considerable number of electronic components. Multi-frequency (MF) dialing is controlled by 12 dialing keys, and there are 10 service keys for dial repetition, three party conference, short dialing, etc. To prevent disturbances in the earphone when a key is activated, transistor T1, which is part of a side tone protection circuit, is cut off. Activation of any one of the 22 keys causes a signal to be stored in an MF coder and a storage unit. Hence, only one electrical contact need be provided for the keys. The MF coder controls an MF generator, by means of which a multi-frequency signal is applied to the subscriber line.

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Electronic Subscriber Set With Improved Flashing

The figure is a schematic of the circuit for a telephone subscriber set using a considerable number of electronic components. Multi-frequency (MF) dialing is controlled by 12 dialing keys, and there are 10 service keys for dial repetition, three party conference, short dialing, etc. To prevent disturbances in the earphone when a key is activated, transistor T1, which is part of a side tone protection circuit, is cut off. Activation of any one of the 22 keys causes a signal to be stored in an MF coder and a storage unit. Hence, only one electrical contact need be provided for the keys. The MF coder controls an MF generator, by means of which a multi-frequency signal is applied to the subscriber line.

The electronic circuitry in the subscriber set is fed by a positive supply voltage Up generated by transistor T2 of a stabilized supply voltage circuit schematically represented in block 2. This supply voltage circuit ensures that DC and AC circuits are effectively separated.

The figure also shows a flashing circuit 3 with transistor T3 which is normally conductive. Transistor T3 can be cut off either by a flashing timer controlled by the 10 service keys or by a detection and discriminator circuit 4. Flashing circuit 3 includes an optical coupler and a dialing tone transistor T4. Transistor T4 is cut off by means of a negative supply voltage Un generated, for example, by rectifying a high frequency signal of, say, 100 k...