IGITAL SWITCHING TECHNIQUE FOR USE ON COMMUNICATIONS CIRCUITS

• US 3,814,840 A
• Filed: 05/08/1972
• Issued: 06/04/1974
• Est. Priority Date: 05/08/1972
• Status: Expired due to Term

• Current Assignee: General Signal Corporation (SPX Corporation)
• Original Assignee: Lubarsky A, Warner G
• Inventors: LUBARSKY A, WARNER G
• Application Number:
  US05/251,354
• Time in Patent Office: 757 Days
• US Class Current: 178/2.00C
• CPC Class Codes: H04M 3/28 Automatic routine testing ; Fault testing; Installation testing; Test methods, test equipment or test arrangements therefor

Abstract

A plurality of remote switching modules are positioned along a telephone communication circuit and are responsive to signals sent by a control unit along the same circuit. The control unit signal includes a plurality of bursts of bipolar digital pulses having a certain format with timed spaces between each burst of pulses. Each remote module counts the pulses received from the control unit through the communications circuit. One of the modules responds when addressed with a burst of pulses of a number for which the module has been uniquely programmed. When a given module has been addressed, another burst of pulses tells the addressed module what switching function to perform.

Claims

1. A method of signaling from a controlling location along a communication circuit a programmed switching function at a selected one of a plurality of remote locations along said communication circuit, comprising the steps of:

sending an address burst of a given number of pulses along the communication circuit from the controlling location to address a particular remote location, a repetition period of said pulses being significantly longer than the duration of each pulse itself, said address burst being preceded and followed by a space characterized by an absence of pulses for a time equal to at least two pulse repetition periods, counting the number of pulses of the address buRst within the communication circuit at each of the remote locations, said address burst pulse counting including the steps of;

comparing the signal level of the communication circuit at the remote locations with a threshold signal level, generating an internal pulse having a duration slightly less than the length of the pulse repetition period each time the signal level of the communication circuit exceeds said threshold signal level, and advancing a binary counter each time said internal pulse is generated, detecting said space after the address burst at each of the remote locations, comparing the address count with a preset unique address at each remote location upon detection of said space, thereby to address a single remote location following a burst of address pulse of a number equal to the preset unique address of said single remote location, sending a function burst of a given number of pulses along said communication circuit from the controlling location to command the addressed remote location to perform a specific function, a repetition period of said pulses being significantly longer than the duration of each pulse itself, said function burst being initiated immediately after said space following the address burst and being followed by another space that is characterized by an absence of pulses for a time equal to at least two pulse repetition periods, counting the number of pulses of said function burst within the communication circuit at the addressed location, said function burst pulse counting including the steps of;

comparing the signal level of the communication circuit at the remote locations with a threshold signal level, generating an internal pulse having a duration slightly less than the length of the pulse repetition period each time the signal level of the communication circuit exceeds said threshold signal level, and advancing a binary counter each time said internal pulse is generated, detecting said space after the function burst at the addressed location, and performing a unique programmed switching function at the addressed remote location according to the number of pulses counted in said function burst after detection of said space after the function burst.

2. The method according to claim 1 wherein the threshold signal level is increased above a minimum level in response to a strong signal level in the communication circuit.

3. A switching module for installation at remote locations along a communication circuit, comprising:

input circuits for connection of the switching module to the communication circuit, means for generating a threshold signal level that varies up and down in response to similar changes in average signal level in the communications circuit, comparator means responsive to a signal level in the communications circuit through said input circuits and further responsive to said threshold signal level for generating at its output a first signal when the communications circuit signal level exceeds said threshold signal level and a second level when the communications circuit signal level is below said threshold signal level, means responsive to the output of the comparator means for generating a pulse each time said comparator means changes from its second to its first output signal, a digital counter connected to increment a preset amount in response to each pulse of the pulse generating means, and means responsive to an output of said counter for switching to a particular distinct state according to the count of said counter.

4. The switching module according to claim 3 wherein said threshold signal level varying means includes means for increasing the threshold signal level with a lower time constant in response to an increasing communications circuit signal level than a time constant of a decreasing threshold signal that occurs in response to a decreasing signal level in the communications circuit.

5. A switching moduLe for installation on a communication circuit, comprising, input circuits for connection of the switching module to the communication circuit, a binary counter connected to said circuits in a manner that the counter increments a given fixed amount for each pulse to be detected in the communication circuit, the count of said counter being represented in binary form at a plurality of output lines with one binary bit signal carried by each line, a binary storage circuit connected to less than all of said plurality of output lines of the counter as a memory for switching functions to be performed in response to certain combinations of signals in said less than all said plurality of output lines, a logic circuit operably connected to some other of the counter output lines to permit transfer of the binary bit signals in said less than all of said plurality of output lines to said binary storage circuit only when said some other of the counter output lines are in a predetermined state.

6. A method of conveying a message in the form of a number of pulses along a communication circuit, comprising:

sending a burst of a given number of consecutively recurring pulses along the communication circuit from a controlling location to a remote location, a repetition period of said pulses being significantly longer than the duration of each pulse itself, comparing the signal level of the communication circuit at the remote location with a threshold signal level, generating a pulse at the remote location that has a duration slightly less than the length of the pulse repetition period each time the signal level of the communication circuit at the remote location exceeds said threshold signal level, and advancing a digital counter of predetermined amount in response to each of said generated pulses, whereby a count of the number of pulses of said burst in binary number form is presented across a plurality of output lines of the digital counter.

7. The method according to claim 6 wherein the pulse repetition period is significantly longer than the duration of the pulses.

8. The method according to claim 6 wherein said communication circuit has a transmission bandwidth within a voice frequency range of substantially 300 to 3,000 Hz. and wherein the step of sending a burst of pulses includes sending the pulses in bipolar form with their duration being within the bandwidth of said communication circuit.

9. The method according to claim 6 wherein the threshold voltage level is increased above a minimum level in response to a strong signal level in the communication circuit.