Battery charger control circuit for telephone transmission systems

DETAILED DESCRIPTION Referring to the drawing, a telephone transmission system incorporating the principles of this invention is shown to comprise a central office or central office station 20, a subscriber's station 22 which is located remotely from the central office 20, a subscriber's telephone 23 which is located at the subscriber's station, and a two-conductor telephone transmission line 24 having transmission conductors 26 and 28 which provide the usual connection between telephone 23 and the central office 20.
The central office equipment may be conventional and includes, among other things, a central office d.
c.
power supply source 30.
Source 30 is connected across conductors 26 and 28 through the coils of a line relay 32 so that the terminal or output voltage of source 30 is applied across conductors 26 and 28 at the central office.
Line relay 32 is conventionally connected to the switching equipment in the central office.
Source 30 may be any suitable means for providing d.
c.
voltage.
For example, source 30 may be a d.
c.
generator, a rectifier or a battery.
Source 30, which is customarily referred to as the central office battery, is preferably a substantially constant voltage source and usually supplies power for operating central office equipment.
The remote storage battery in this invention is indicated at 34 and is connected across the load or output terminal of a battery charger 36.
The battery charger control circuit of this invention is indicated at 40 and is connected between line 24 and charger 36 to draw current from source 30 for powering charger 36.
Battery 34 may be any suitable, conventional re-chargeable construction.
For example, battery 34 may be of the nickel cadmium type.
Charger 36 may be any suitable conventional electrical circuit for charging battery 34.
Battery 34 may be utilized to power any selected equipment which is normally located remotely from central office 20 and which is capable of operation by current drawn from battery 34.
For example, battery 34 may be utilized to power one or more of the following pieces of equipment: the unshown ringer in telephone 23, unshown subscriber carrier apparatus in the event that the telephone transmission system is a subscriber carrier system, and an amplifier 42 for a telephone loudspeaker 44