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Claims  |
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What is claimed:
1. A control system for controlling the application of power to one or more
power-dependent units at a remote site in accordance with power control
messages transmitted from a local site to the remote site over an
intersite communications channel which couples the two sites where the
inter-site communications channel also carries other messages, the system
comprising:
a power line extending through the remote site for supplying power to the
power-dependent units;
master control means, located at the remote site and operatively coupled to
the remote site power line, for transmitting power controlling signals
through the remote site power line, the power controlling signals defining
when and which of the one or more power-dependent units will receive power
from the power line, the master control means having a master receiving
port for receiving operation control commands which control operations of
the master control means; and
message routing means, located at the remote site and having first and
second message routing channels both coupled to the inter-site
communications channel, for receiving messages from the local site and
selectively routing each received message onto one or the other of the
first and second message routing channels,
the first of the message routing channels including power-message relaying
means, coupled to the master receiving port of the master control means,
for generating in response to power control message received from the
local site and for transmitting to the master control means the operation
control commands which control the operations of the master control means,
the second message routing channel being not coupled to the master
receiving port of the master control means so that messages routed onto
the second message routing channel cannot alter the operations of the
master control means.
2. The control system of claim 1 further comprising
one or more slave power control means located at the remote site, the one
or more slave power control means being coupled to the remote site power
line and the power-dependent units, for receiving the power controlling
signals transmitted by the master power control means and for selectively
supplying power from the power line to the one or more power-dependent
units in response to the power controlling signals.
3. The control system of claim 2
wherein the message routing means selectively routes received ones of the
other messages onto the second message routing channel and
the control system further comprises a remote computer located at the
remote site, the remote computer having a power connector connected to one
of the slave power control means and a data communication line coupled to
the second message routing channel of the message routing means for
carrying the received ones of the other messages to the remote computer.
4. The control system of claim 1
wherein a duplicate message routing means, having a structure substantially
identical to the remote site message routing means is located at the local
site, the duplicate message routing means including a local first message
routing channel and a local second message routing channel both coupled to
the inter-site communications channel, and
wherein only one of said local first and local second channels carries all
messages transmitted from the local site to the remote site.
5. The system of claim 4 wherein one or more remote-site computers are
provided at the remote site and the second message routing channel of the
remote site message routing means is coupled to the one or more remote
site computers.
6. A method for controlling power application to electronic equipment
located at a remote site in accordance with power-control messages
transmitted over a shared communications line from a local site, where the
shared communications line carries non-power messages in addition to the
power-control messages, the method comprising the steps of:
defining at least two channels at the remote site, each channel being
operatively coupled to the shared communications line to receive messages
transmitted to the remote site over the shared communications line, at
least one of the channels being a power control channel;
forming a message at the local site;
attaching message-routing information to the formed message, the message
routing information designating one of the at least two channels as a
target channel;
transmitting the formed message with the attached message-routing
information from the local site to the remote site over the shared
communications line; and
at the remote site, routing the transmitted message according to its
message routing information onto the one channel designated as the target
channel.
7. The method of claim 6 wherein the formed message is a power-control
message and the message routing information designates the power control
channel as the target channel.
8. The method of claim 6 wherein the formed message is a non-power message
and the message routing information designates a channel other than the
power control channel as its target.
9. The method of claim 6 further comprising the step of:
encrypting the combination of the formed message and the message routing
information before transmitting it over the shared communications line.
10. The method of claim 9 further comprising the step of:
compressing said encrypted combination before transmitting it over the
shared communications line.
11. The method of claim 6 further comprising the step of:
attaching error detection information at the local site to the combination
of the formed message and the message routing information before
transmitting it over the shared communications lines;
testing the error detection information at the remote site to detect a
transmission error; and
performing the routing step at the remote site only if no transmission
error is detected.
12. The control system of claim 1 further comprising:
message encrypting means at the local site for encrypting each message
before the message is transmitted over the inter-site communications
channel and
message decrypting means at the remote site for decrypting each received
message.
13. The control system of claim 1 further comprising:
message encrypting means at the remote site for encrypting each message
before the message is transmitted over the inter-site communications
channel and
message decrypting means at the local site for decrypting each received
message.
14. A remote control system where a remote site is coupled to a local site
by an inter-site communications channel,
the remote control system being for selectively applying power at the
remote site to one or more remote-site devices in accordance with power
control messages transmitted from the local site, the system comprising at
the remote site:
an AC power line for supplying alternating current power at the remote
site;
a master power-control unit coupled to the AC power line;
one or more power-control slave units coupled to the AC power line;
a multi-channel modem, coupling the remote-site end of the inter-site
communications channel to the master power-control unit and to the one or
more remote-site devices, the multi-channel modem having one channel
dedicated to transmitting control signals between the master power-control
unit and the local site and a second channel dedicated to transmitting
other signals between the one or more remote-site devices and the local
site.
15. The remote control system of claim 14
wherein the master power-control unit has a predetermined first command
format;
wherein the local site includes a command issuing computer whose power
commands follow a predetermined second command format; and
wherein the local site further includes format conversion means for
converting commands issued by the local site computer from the first
command format to the second command format.
16. A remote control system for enabling a local site computer to control
the application of power to and the operations of a remote site computer
by sending power control and operation control signals over an inter-site
communications channel coupling the local site to the remote site, the
system comprising:
a local modem located at the local site for coupling the local site
computer to the inter-site communications channel;
a remote modem located at the remote site, the remote modem having an
inter-site port coupled to the inter-site communications channel, a first
port coupled to the remote site computer, a second port, and signal
routing means for routing signals passing through the inter-site port to
one or the other of the first and second remote modem ports; and
programmable power supplying means located at the remote site and coupled
to the second port of the remote modem for receiving power control signals
from the second port of the remote modem, the power supplying means being
further coupled to the remote site computer for selectively supplying
power to the remote site computer in accordance with the power control
signals received from the second port of the remote modem.
17. The system of claim 16 wherein the inter-site communications channel
includes a telephone line.
18. The system of claim 16 wherein the programmable power supplying means
includes an AC power line, one or more slave units coupled to the power
line and a master unit coupled to the power line for controlling the slave
units by way of signals transmitted over the power line.
19. The system of claim 16 further comprising a second remote site computer
coupled to the first port of the remote modem for receiving operation
control signals from the first port, the second remote site computer being
further coupled to the power supplying means for receiving power therefrom
at selected times.
20. A method of supplying power to and controlling the operations of a
remote site computer from a local site computer, the method comprising the
steps of:
providing a local modem at the local site coupled to the local site
computer;
providing a multi-channel remote modem at the remote site with a first
channel of the remote modem being coupled to an operations controlling
port of the remote site computer;
providing a programmable power supply at the remote site coupled to a
second channel of the remote site modem for selectively supplying power to
the remote site computer in accordance with power control signals
conducted by the second channel;
commanding the local modem to call the remote modem;
when the remote modem answers commanding the remote modem, by way of
command messages sent through the local modem, to route received messages
to the second channel of the remote modem;
sending a power-on command from the local computer through the local modem
and through the second channel of the remote modem for causing the remote
site power supply to supply power to the remote site computer;
after power is supplied to the remote site computer, commanding the remote
modem to route messages between the local modem and the first channel of
the remote modem; and
sending operation control signals to operate the turned-on remote computer
over the first channel of the remote modem.
21. The method of claim 20 further comprising the steps of:
encrypting and compressing messages within the local modem before sending
them to the remote modem; and
decompressing and decrypting messages received from the local modem within
the remote modem.
22. The method of claim 20 further comprising the steps of:
encrypting and compressing messages within the remote modem before sending
them to the local modem; and
decompressing and decrypting messages received from the remote modem within
the local modem.
23. The method claim 20 further comprising the steps of:
after operation control signals are sent over the first channel of the
remote modem, commanding the remote modem to route messages between the
local modem and the second channel of the remote modem; and
sending a power-off command from the local computer through the local modem
and through the second channel of the remote modem for causing the remote
site power supply to discontinue the supply of power to the remote site
computer. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention disclosed here relates generally to remote control of
computerized equipment and more specifically to remote control of the
power supply of a computer system and/or other electrical devices.
2. DESCRIPTION OF THE RELEVANT ART
The advantages of being able to turn on and off the power supply of a
computer system located at a remote site are well known. U.S. Pat. No.
4,206,444 "Remote Power Controller Utilizing Communication Lines" issued
June 3, 1980 to Ferlan, for example, discusses the advantages of reducing
power consumption and the danger of unintended turn-on. The Ferlan
disclosure is incorporated herein by reference. According to the Ferlan
patent, a comparator is interposed at the remote site between a modem and
a gate activated power relay. The comparator scans through incoming serial
signals from the modem searching for a predetermined sequence, and when
this sequence is detected, the gate controlled relay is turned either on
or off to thereby supply electrical power to a computer power unit.
A disadvantageous aspect of the Ferlan design is that incoming messages to
the modem must be restricted so that the predetermined power turn-on or
turn-off sequence is not included when such turn-on or turn-off is not
desired. It is possible for binary bit stream to randomly include this
sequence, and if such a sequence is randomly generated, an undesirable
activation of the power controlling relay may take place.
Another disadvantage of the Ferlan design is that the receiving modem at
the remote site needs to be closely placed to the power control unit and
to the computer which is to be turned on or off. This limits the
flexibility of users in being able to move their computer equipment from
one location to another within the remote site without having to also move
the receiving modem and its adjunctive telephone wires.
Other works in the field of remote control which Applicant is aware of
include U.S. Pat. No. 4,701,946 "Device for Controlling the Application of
Power to a Computer" issued Oct. 20, 1987 to Oliva, et al.; U.S. Pat. No.
4,723,269 "Method and Apparatus for Power-Up of Unattended Computer"
issued Feb. 2, 1988 to Summerlin; U.S. Pat. No. 4,647,721 "Telephone
Activated Power Controller" issued Mar. 3, 1987 to Busam, et al.; U.S.
Pat. No. 4,809,163 "Computer System with Power Control Based on the
Operational Status of Terminals" issued Feb. 28, 1989 to Hirosawa, et al.;
and U.S. Pat. No. 4,812,963 "Plural Cooking Computer Communication System"
issued Mar. 14, 1989 to Albrecht, et al.
SUMMARY OF THE INVENTION
It is an object of the invention to provide users with a low cost and
flexible system for controlling power to computerized equipment and/or
other electrical devices at a remote site.
In accordance with a first aspect of the invention, there is provided a
master power-control unit, coupled to the AC power lines of the remote
site for transmitting power control signals along the AC line to one or
more corresponding power-control slave units, which are also coupled to
the remote AC line for receiving control signals from the master unit. The
master power-control unit is operatively coupled to one channel of a
multi-channel modem. The one channel of the multi-channel modem is
dedicated to transmitting control signals between the master power-control
unit and a local-site control system located away from the remote site.
Because the one channel is dedicated to transmitting only signals which
are for control of the master power unit and its slaves, there is no
danger that other transmissions will trigger an unintended action by the
master power-control unit.
In accordance with a second aspect of the invention, the multi-channel
modem at the remote site includes header detection means for detecting a
message-routing field in a header portion of incoming message packets and
for directing message packets intended for the one-channel which is
coupled to the master power control unit, to that one channel, while
directing messages intended for other channels (as indicated by the
message-routing field) to the other channels.
In accordance with a further aspect of the invention, a local-site computer
system is provided for converting English-like commands such as "TURN ON
APPLIANCE NUMBER 1" into binary signals of a format matching the control
format of the master power-control unit and for generating a message
packet header which includes message-routing information for selecting the
one channel at the remote site which is dedicated to the master
power-control unit. The local-site computer system is further provided
with switching means for automatically switching the message-routing
information (field) of the header from one designating the channel of the
master power-control unit of the remote site to one designating another
channel at the remote site, which for example, is coupled to a remote-site
computer whose power is controlled by a slave power unit that is
responsive to control signals from the master power-control unit.
In accordance with a further aspect of the invention, the modems at the
local and remote sites are provided with a multiplicity of bypassable
functions including: a first function for adding a router header and
optional router tail to a message which is to be routed; a second function
for encrypting a core message packet which includes the message body and
optionally includes a router header and tail; a third function for
compressing and/or adding a protocol envelope to the optionally-encrypted
core message packet; a fourth function for optionally stripping off the
protocol envelope of a protocol enveloped and compressed message core,
decompressing the core, and for performing any error correction or
handshaking subfunctions associated with the protocol; a fifth function
for optionally decrypting the optionally encrypted message core; and a
sixth function for optionally stripping off the router header and tail
portions of the message core and routing the message body according to the
routing-field information within its router header. A seventh function is
further provided for optionally converting a message from an English-like
command structure to one matching the format of a preselected master
power-control unit. Other aspects of the invention will become apparent
from the below detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a remote power control system in accordance
with the invention.
FIG. 2 is a block diagram of a MultiFunction Encryptor (MFE) device
according to the invention.
FIG. 3 is a flow chart of the operating modes of the local-site and
remote-site modems shown in FIG. 1.
FIGS. 4A-4G show respectively: (A) an MFE to MFE secured connection, (B) a
standard non-secured communications connection, (C) a self-encrypt/decrypt
connection, (D) a high-speed security connection, (E) a secured MFE to MFE
multiplexed connection, (F) a secured multipoint connection, and (G) a
secured home control connection.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following is a detailed description of the best modes presently
contemplated by the inventor for carrying out the invention. It is to be
understood that these modes are merely exemplary of the spirit and
principles of the invention and that the description of these modes should
not be taken in a limiting sense.
Referring to FIG. 1, a remote control system 100 in accordance with the
invention is shown. The control system 100 allows a user (not shown) at a
local site 110 such as a hotel room or a satellite office to control
computerized equipment at a remote site 120 (i.e., home or base office)
using an ordinary local to remote site communications channel 119 such as
a telephone network.
At the local site 110, a local computer 111 (i.e., a so-called "laptop" or
"portable" microcomputer) is operatively coupled (i.e., through an RS-232
serial communication link) by way of a first modem channel 113a to a local
modem 113 which in turn is coupled through appropriate network interface
means 115 (i.e., Bell 103) to the local-remote communications channel 119.
The local modem 113 is preferably a multi-function encryptor (MFE) device,
as shown in FIG. 2, having a second modem channel 113b to which no
connection (N.C.) needs to be made for the arrangement 100 of FIG. 1. The
MFE device will be described in detail later.
At the remote site 120, a corresponding network interface means 125 (i.e.,
Bell 103) connects the local-remote communications channel 119 to a
multi-channel remote modem 123 (again, preferably an MFE device as shown
in FIG. 2 which is to be described later). One channel 123b of the
multi-channel remote modem 123 is coupled to a master power-control unit
131 such as an X10.TM. "Powerhouse" master power module available from
X-10 (USA) Inc. of Northvale, NJ. Those skilled in the art will recognize
that the X-10.TM. system is one of many different through-the-power-line
control systems available from different vendors. Additional examples of
master power-control units and their slaves may be found for example in
U.S. Pat. No. 4,677,566 "Power Control Network For Multiple Digital
Modules", issued June 30, 1987 to Whittaker et al.; U.S. Pat. No.
4,643,062 "Power Control Network Using Reliable Protocol", issued Jan. 6,
1987 to Jeppesen et al.; and U.S. Pat. No. 4,864,589 "Spread Spectrum
Power Line Communication", issued Sept. 5, 1989 to Endo, the disclosures
of all said patents being incorporated herein by reference. In addition to
through-the-power-line control systems at the remote site, it is within the
contemplation of the present invention to use other through-the-remote site
communications schemes such as employing radio links, sharing telephone
wiring or computer network wiring for transmitting control signals from a
master unit (131) to slave units (141, 143, 145, etc.).
A second channel 123a of the remote modem 123 is coupled to a first
remote-site computer 121 (i.e., a so-called "desktop" microcomputer or
"engineering workstation" or "minicomputer" or "mainframe" that is more
powerful computing-wise than the local-site computer 111). The remote
modem 123 to remote computer 121 coupling is preferably a serial channel
(123a) which, by way of example, can be an RS-232 serial link. The second
channel 123a conducts binary transmissions between the first remote-site
computer 121 and the remote modem 123.
The master power-control unit 131 has a power connector 132 plugged into an
AC power line 130 which extends through the remote site 120. A first slave
unit 141 (preferably an X10 slave module), which may be located a
substantial distance (i.e., more than 12 feet) away from the master unit
131, has its corresponding power connector 142 plugged into the
remote-site power line 130 for communicating therethrough with the master
power-control unit 131. The remote computer 121 has its corresponding
power connector 122 plugged into the first slave power control unit 141 so
that power may be selectively turned on or off to the remote computer 121
when the master power-control unit 131 issues an appropriate command
signal onto the remote-site power line 130.
As shown in FIG. 1, additional pieces of equipment may be further connected
to the remote-site power line 130 by way of additional slave power-control
modules. A remote-site printer 151 is shown to have its power connector
152 plugged into a second slave module 143 whose respective power
connector 144 is plugged into the remote-site power line 130. The remote
printer 151 is further operatively coupled by way of an RS-232 or other
communications link to the remote computer 121 for receiving print
instructions from the remote computer 121. When the remote printer 151 is
not needed, its power supply may be shut off by way of commands sent from
the master unit 131 to the slave module 143 through the remote-site power
line 130 in order to conserve power and increase the operating life of the
printer 151. Additional remote appliances 161 such as memory backup devices
(i.e., mass storage such as a high capacity disk drive) and so forth may be
also be operatively coupled to the remote computer 121 and the power
connectors 162 of these additional appliances 161 may be respectively
coupled to the remote power line 130 through further slave units 145
having respective connectors 146 plugged into the remote power line 130.
The remote site computer 121 is shown to be further coupled to a so-called
"local area network" (LAN) to thereby provide a user at the local site 110
with access to the resources (software and/or hardware) of the LAN.
In addition to equipment which communicates with the remote computer 121,
there may be further provided additional computer equipment which is not
cooperatively coupled to the remote computer 121. By way of example, a
second remote-site computer 171, which is located far away (i.e., 12 or
more feet) from the first remote computer 121, may have its respective
power connector 172 plugged into a fourth slave module 147 whose
corresponding electrical connector 148 is also operatively coupled to the
remote-site AC power line 130. The second channel 123a of the remote modem
123 may be coupled to this second remote computer 171, if desired, so that
communication may take place between the local site 110 and the second
remote computer 171 when the latter computer is powered up. The first
remote computer 121 is not powered up at this time so that the second
channel 123a may be shared by both the first and second remote computers,
121 and 171, on a one at a time basis. Alternatively, a separate
communications channel (i.e., 123c not shown) may be provided on the
remote modem 123 for exclusive use by the second remote computer 171 so
that contention for a single channel (123a) does not take place between
the first and second remote computers, 121 and 171.
Users may further wish to attach equipment such as a video cassette
recorder (VCR) 181 to the system 100 so that the VCR 181 may be
selectively turned on or off by way of having its power connector 182
plugged into a fifth slave module 149 whose corresponding power connector
150 is plugged into the remote power line 130. The VCR 181 may be
operatively coupled to one of the remote computers (i.e., the second
remote computer 171) so that a specific operation of the VCR 181 (i.e.,
play, record, rewind, etc.) may be selected from the local site 110 when
desired by way of communication through the remote computer (i.e., 171).
The master power-control unit 131 preferably includes an internal
programmable timer (not shown) so that a command can be sent from the
local site 110 to the master power-control unit 131 to turn on or off any
one of its slave modules at a prespecified time after the time of the
command transmission from the local site 110.
Furthermore, lighting devices 191 provided at the remote site 120 may be
turned on, off or dimmed by connecting these lighting devices 191 through
one or more appropriate connectors 192 to yet a further set of one or more
slave modules 193 whose corresponding power connectors 194 are operatively
coupled to the remote power line 130 for receiving commands from the
master power module 131. The lighting devices 191 may be commanded from
the local site 110 to turn on, off or dim at random times in order to give
the remote site 120 the appearance of being occupied and to thereby provide
security for the remote site 120. The timings of such events may be
controlled by setting from the local site 110, the internal timer (not
shown) of the master power-control unit 131. If desired, additional
security may be provided to the remote site 120 by having a tape recorder
183 randomly powered up to provide noise at the remote site 120 as an
additional security measure. Furthermore, to secure messages on an
automatic telephone operating machine (i.e., automatic telephone answering
machine) 195, power is controllably applied to a telephone
answering/playback part of the machine 195 by way of connecting the power
connector 196 of the telephone operating machine 195 to a slave power unit
197 whose corresponding power connector 198 is coupled to the remote power
line 130. The telephone answering/playback portion of the telephone
operating machine 195 will not be able to playback recorded messages
through a telephone network 199, 200, 201 unless power is supplied to the
telephone operating machine 195 by way of its slave power module 197. The
telephone operating machine 195 may optionally include an auto-dial unit
which can automatically place calls out through the remote-site telephone
equipment 199 to contact prespecified parties (i.e., police, fire
department, doctor, etc.) in the event of an emergency and to play to such
parties a prerecorded message stored in a tape-unit (not shown) of the
telephone operating machine 195. As indicated in FIG. 1, one of the
remote-site computers 121 or 171 could be coupled by way of a link 202 to
such an emergency auto-dialer (195) in order to monitor or control its
state and report the status of the machine 195 to the local site 110 or to
activate the machine 195 according to commands received from the local site
110. Moreover, alarm systems 203 for detecting and reporting intrusion or
fire/gas at the remote site 120 may be coupled to the telephone operating
machine 195 for automatically initiating autodial operations when an
emergent condition is detected.
With the system configuration 100 of FIG. 1, a user at the local site 110
may choose to turn on, off or dim the power to any of a large number of
appliances located at the remote site 120. Data files stored within memory
components of the remote computers 121, 171 (or in the resources of the LAN
to which the computers 121, 171 can be connected) or other mass storage
devices 161, are secured from probing by unauthorized persons who might
gain access to the remote modem 123 (assumed to be always ON and ready to
pick up its telephone receiver) through the communications channel 119.
Until an appropriate power turn on command is sent through the remote
modem 123 to the master power unit 131 of the remote site 120 to thereby
apply operating power to such data file supporting devices (i.e. 121, 161,
171, LAN), these devices will not respond to requests sent through the
remote modem 123 for data access. Preferably, the local modem 113 and
remote modem 123 have corresponding data encryption and decryption devices
(as will be described with reference to FIG. 2) so that only those users
who are in possession of an appropriate encryption/decryption key may be
able to send intelligent control signals to the master control unit 131
and/or to the remote computers 121 and 171 for activating these devices.
Additionally, with the configuration 100 of FIG. 1, a user at the remote
site 120 can also use the remote MFE 123 to control power application at
the remote site 120 by sending appropriate commands from computer 121
through MFE 123 to power unit 131.
Referring to FIG. 2, the operations of the local and remote modems, 113 and
123, will now be explained in more detail. Each of the modems, 113 and 123,
is preferably designed according to the MFE structure shown in FIG. 2. An
MFE (multi-function encryptor) device as shown in FIG. 2 includes a mode
selecting means (i.e., switch) SW-1 for placing the MFE in one of at least
three modes: a command mode, a data mode and a remote control mode. The
mode selecting switch SW-1 is responsive to a mode-select signal sent from
a configuration module 250 of the MFE along mode-select line 252. When
power is first applied to the MFE or the MFE is reset, the configuration
module 250 performs a system initialization operation in which a plurality
of function-bypass switches (SW-2 to SW-12), multiplexers (i.e., 264, 290,
291) and latches (i.e., 256, 259) are placed in initial states, as will be
understood shortly. Upon initialization, the configuration module 250
further issues a signal along mode-selecting line 252 to place the
mode-selecting switch SW-1 in the command ("Cmnd") mode.
In the command mode, data from a first channel (chnl A) of the MFE is
routed to the configuration module 250 for allowing an external control
computer (111 at the local site and/or 121 at the remote site) to send
configuration commands to the configuration module 250 for configuring a
multiplicity of other units (i.e., switches SW-1 through SW-12, SW-14,
latches 256 and 259, function units 270-275 and 281-285, error module 296
and multiplexers 264, 290 and 291) within the MFE. As shown in FIG. 2, the
MFE comprises a multiplicity of interconnectable functional units, i.e. 270
through 275 and 281 through 285, whose functions may be selected or
bypassed by appropriate setting of corresponding function-bypass switches
SW-2 through SW-12. The MFE further comprises a series of multiplexers and
other signal routing switches (264, 290, 291 and SW-14) for routing
messages from a variety of sources to a variety of destinations as will be
described below. Moreover, the MFE comprises a set of escape sequence
detectors, 254 and 262, for detecting the presence of escape sequences on
respective lines, 253 and 263, as well as a remote response detector 295
for detecting a response message (i.e., master power unit acknowledge
signal) sent from a unit (131) at the remote site and an error detecting,
reporting and handling module 296 for detecting the occurrence of
transmission errors, recovering from those errors, and reporting the same
to an appropriate monitor means (i.e. the local computer 111 or remote
computer 121).
The operations of the MFE may be best explained by walking through its
various operating modes. After power-up of the MFE, one of the
configuration commands which the configuration module 250 may receive in
the initial command mode ("cmnd") is a command to set or reset an internal
remote-control latch (RC latch) 256. When the RC latch 256 is reset to
output a logic low to AND gates 257 and 258; and further an escape enable
latch (Esc En) 259 of the MFE is set to output a logic high to the AND
gates 257 and 258; the MFE is configured to operate as a standard modem
and to switch back and forth between the command (Cmnd) and data modes
upon receipt of appropriate command sequences (i.e. ATA, ATD, ATO, which
respectively are Hayes.RTM. recognized command words for answer, dial and
go on-line) when the MFE is in the command mode or upon receipt of a
suitable escape sequence (i.e. pause-+++-pause) when the MFE is in the
data mode. The mode selecting switch SW-1 remains in the command setting
until | | |
