Service integrated digital transmission system operating in time multiplex

A terminal device for use in a service integrated, multiplex digital signal transmission system which includes an optical fiber waveguide line connected to the terminal for conducting a light signal and a member for modulating the light signal with multiplexed narrowband signals and multiplexed broadband signals, the terminal device including narrowband signal processing devices connected to the optical fiber waveguide line for transforming only narrowband signals between a multiplexed state and a demultiplexed state, broadband signal processing devices connected to the optical fiber waveguide line for transforming only broadband signals between a multiplexed state and a demultiplexed state, a member connected for normally supplying operating power to said signal processing means from local utility mains, a charge accumulator for supplying operating power in the event of interruption of the power supply by the local mains, and elements connected for switching the terminal device to effect signal transmission at a reduced bit rate in the event of such local power interruption. The terminal device further includes a signal detector connected for monitoring signal transmission and connected to the switching elements for causing operating power to be supplied from the accumulator for signal processing only during times when signal transmission is taking place.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a service integrated digital 
time multiplexed transmission system. 
In copending U.S. application Ser. No. 324,662 filed by Hans-Jurgen Schmack 
and Erich Rauth on Nov. 24th, 1981, and claiming priority of German Patent 
application P No. 30 44 605.0 of Nov. 27th, 1980, there is disclosed a 
transmission system of the above type having a commercial power buffered 
accumulator, or battery, which takes over the supply of operating power 
when there is an interruption in commercial power and, in such case, 
transmission over the optical fiber waveguide system is adjusted to a 
reduced bit rate. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to save even more energy in a 
system of this type so as to be able to bridge a commercial power 
interruption for an even longer period of time. 
It is a further object of the present invention to terminate connection of 
even narrowband transmission and reception components to the charge 
accumulator when no narrowband signals are being transmitted or received. 
The above and other objects are achieved in accordance with the present 
invention by providing a signal detector which is responsive to narrowband 
signals being received or transmitted during a power supply outage. The 
detector operates a switch which disconnects the conventional charge 
accumulator from the narrowband transmitter and receiver when no 
transmitted or received signals are present in order to reduce further the 
current drain on the battery. 
With the transmission system according to the present invention it is 
possible to maintain emergency operation over longer periods of time if 
there is an interruption in commercial power supply and to do this in an 
energy saving manner. With the present invention it is also possible to 
use a battery, or charge accumulator, which has a smaller capacity and 
thus a smaller volume. The additional expense to implement the invention 
is relatively small.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The upper portion of the FIG. 1 shows the receiving portion and the lower 
part the transmitting portion device at a subscriber terminal. The lines 
provided with arrows carrying information signals in the direction of the 
associated arrows, and the lines not associated with arrows carry 
operating power supply. 
The receiving portion includes a light receiver in the form of a photodiode 
ED, a main amplifier V1, a broadband branch composed of an amplifier V2, a 
broadband signal regenerator REGB and a broadband demultiplexer BB-DMUX, 
and a narrowband branch composed of an amplifier V3, a narrowband signal 
regenerator REGS and a narrowband demultiplexer SB-DMUX. 
The circuit units of the broadband branch are fed directly via a power 
supply unit NG by the local utility power mains, while the narrowband 
units are fed via a switch S1 by a buffer battery PB, the latter being 
maintained charged by the mains power via a diode D. Receiver diode ED and 
main amplifier V1, as well as a signal detector SDT provided according to 
the invention, are fed directly and constantly by the battery PB. The 
signal detector SDT monitors an incoming narrowband multiplex signal ISDN 
and detects when the associated subscriber is being called, which causes 
the switch S1 to be actuated and the narrowband circuit units to be 
switched on. 
Advantageously the signal detector SDT is designed in such a manner that it 
performs an integration of the incoming signals. When a given voltage 
threshold is exceeded, the switch S1 is caused to close. Existing 
broadband signals have no effect since, with a suitable selection of the 
integration constant, a constant voltage results. 
The operation of the narrowband branch is maintained as long as the 
narrowband communication connection is in existence. Once this connection 
is broken, no more signals are transmitted, whereupon the signal detector 
SDT disconnects the narrowband branch, by opening of switch S1, from the 
battery. However, if another narrowband communication is received, the 
narrowband branch is reconnected through switch S1. 
The transmitting portion is treated correspondingly. The broadband branch 
with broadband multiplexer BB-MUX and amplifier V4 are fed by the power 
supply unit NG and therefore will not be in operation when the utility 
power is interrupted. Diode D constitutes a means for preventing current 
flow to the broadband component groups from the battery PB. The narrowband 
branch with narrowband multiplexer SB-MUX and amplifier V5 is supplied 
with power from the buffer battery PB when switch S1 is closed. A 
transmitter diode SD, which may be an LED, is supplied, on the one hand, 
by a current source EBB forming part of the power supply unit NG which 
makes broadband transmissions possible. If utility power is interrupted, 
the current source EBB is switched off, but the current pulses furnished 
by the battery powered amplifier V5 are sufficient to actuate the 
transmitting diode SD in a pure narrowband operation. 
The present invention is of course applicable not only to digital broadband 
and narrowband multiplex signals combined in frequency multiplex but is 
also usable for broadband and narrowband signals which are combined in 
single stage or multistage time multiplex. 
FIG. 2 shows a preferred embodiment of the signal detector SDT. The 
received and transmitted narrow-band signals are applied to the inputs 1 
and 2, respectively. These signals are digital multiplex signals, which 
include speech and date information and are transmitted in an integrated 
speed and date network (ISDN). 
An occurring signal is rectified by decoupling diodes D1 or D2, 
respectively, and is integrated by an integration circuit, consisting of 
resistor R and capacity C. The integrated signal is compared with a 
threshold voltage U.sub.th by an operational amplifier; if it exceeds this 
threshold voltage, a transistor T1 is switched on, activating a relay R1, 
by which the switch S1 is closed. 
Optionally the signal detector SDT has a third input, by which the 
integration circuit is connected to the operating power supply via a third 
decoupling diode D3. If operating power supply is present, the signal 
detector SDT remains in the mode wherein switch S1 is closed. 
The offer components of the terminal device are described in "Contrasting 
Fiber-Optic-Component-Design Requirements in Telecommunications," by 
Personick et al in Proceedings of the IEEE Vol. 68 No. 1 Oct. 1980 and in 
Direct Modification of DHS-Laser, "by Chown et al in Electronics letters 
Vol. 9 No. 2 Jan. 1973. 
It will be understood that the above description of the present invention 
is susceptible to various modifications, changes and adaptations, and the 
same are intended to be comprehended within the meaning and range of 
equivalents of the appended claims.