Patents
Sitemap › H04 - Electric communication technique › H04M - Telephonic communication › H04M 3 - Automatic or semi-automatic exchanges
Patents for H04M 3 - Automatic or semi-automatic exchanges (99,881)
06/1978
06/06/1978US4093829 Single line telephone hold circuit
06/06/1978US4093819 Closed user group facility
05/1978
05/30/1978US4092605 Phase delay simulator
05/16/1978US4090043 Electronic hybrid circuit
05/16/1978US4090038 Audio signal on hold circuit
05/09/1978US4088846 Hold-plus-intercom for single-line stations
05/02/1978US4087646 Dual mode telephone subscriber loop current detector
04/1978
04/25/1978US4086448 Loop-around test circuit for telecommunications lines
04/25/1978US4086446 Emergency announcement system
04/25/1978US4086441 Message-waiting and do-not-disturb communications system
04/25/1978US4086439 Class of line identifier apparatus and method therefor
04/25/1978US4086438 Automatic interconnection system
04/25/1978US4086432 Switching circuit useful in telephone conference systems
04/18/1978US4085298 Measurement of current through a line subject to spurious high potentials
04/18/1978US4085293 Traffic usage recorder
04/18/1978US4085290 Telephone conference amplifier
03/1978
03/28/1978US4081614 Supervised single link telephone system
03/21/1978US4080517 Audio sensory apparatus and method for monitoring indicator lamp status of multi-line telephone instrument
03/14/1978US4079210 Ringing and testing control circuitry for communication systems
03/07/1978US4078158 Call distributing automatic telephone installation
03/07/1978US4077373 Ignition timing control device for an internal combustion engine
02/1978
02/28/1978US4076971 Subscriber line testing system
02/28/1978US4076970 Switching system having a central controller for accessing individual telephone circuits for testing
02/21/1978US4075426 Parallel silent communicator
02/14/1978US4074078 Telephone privacy device
02/07/1978US4072986 Message synthetizer
02/07/1978US4072827 Telephone patching apparatus
02/07/1978US4072825 Hotel/motel automatic control system
01/1978
01/31/1978US4071888 Telephone multiline automatic voice answer system
01/31/1978US4071704 Service generator checking apparatus
01/31/1978US4071698 Telephone system for audio demonstration and marketing of goods or services
01/10/1978US4068101 Method and apparatus for the automatic communication of two telephone subscribers
01/10/1978US4068099 Method of and apparatus for switching service information units in a TDM system
01/03/1978US4066847 Automatic call answering and sequencing system
01/03/1978US4066843 Telephone circuit monitoring system
12/1977
12/20/1977USRE29499 On premise telephone loop tester
12/20/1977US4064377 Electronic hybrid and hybrid repeater
12/20/1977US4064372 Systems for and methods for PBX toll restriction
12/13/1977US4063044 Light responsive monitoring system
11/1977
11/22/1977US4059735 Digital conference system
11/22/1977US4059732 Centralized telephone answering apparatus with remote accessing
11/01/1977US4056698 Special automatic trunk testing arrangement
11/01/1977US4056695 Key telephone line circuit tone-on-hold arrangement
11/01/1977US4056687 Decoupling control arrangement for auxiliary circuits coupled to telephone lines
10/1977
10/25/1977US4055731 Key telephone lamp control circuit
10/18/1977US4054908 Videotelephone conference system
10/18/1977US4054760 Remote testing of telephone loops
10/18/1977US4054759 Subscriber loop verification device and method
10/18/1977US4054757 Conference circuit using PCM techniques
10/18/1977US4054756 Method and apparatus for automating special service call handling
10/18/1977US4054755 Conference circuit for pulse coded modulated telephony
10/11/1977US4053949 Intercept information
10/04/1977US4052569 Emergency call answering system
09/1977
09/27/1977US4051333 Tip and ring conductor voltage tester
09/27/1977US4050165 Teacher-students' intercommunication system
09/20/1977US4049920 Analog signal summing conference circuit
09/20/1977US4049916 Ring detector circuit for centrally located answering and recording equipment
09/20/1977US4049915 Remote access for centrally located answering and recording equipment
09/13/1977US4048647 Solid state disconnect device
09/13/1977US4048452 Automatic call distribution system
09/13/1977US4048451 Arrangement for monitoring live call disposition signals
09/13/1977US4048450 Trunk circuit traffic analyzer
09/13/1977US4048445 Method for through connection check in digital data system
09/06/1977US4047155 Universal data recording system
08/1977
08/30/1977US4045624 Continuous monitoring in carrier telephone systems
08/30/1977US4045623 Short circuit indicator for a terminator matrix
08/30/1977US4045615 Monobus interface circuit using opto-coupled hybrids
08/09/1977US4041255 Switching circuit for telecommunications lines
08/09/1977US4041246 Thyristor cross-point switch with control
08/02/1977US4039768 Pay telephone station monitor system
07/1977
07/26/1977US4038216 Cermets
07/05/1977US4034162 Telephone receiver-off-hook detector
07/05/1977US4034161 Telephone receiver-off-hook detector
06/1977
06/28/1977US4032890 Arrangement for controlling seizure of a connector
06/21/1977US4031328 Conferencing arrangement for use in a PCM system
06/14/1977US4029913 Remote accessing system for telephone lines
06/14/1977US4029909 Operator supervisory circuit for a key telephone system
06/07/1977US4028507 Apparatus for applying particular voltages to three-terminal circuits and measuring resulting current flows for the purpose of determining circuit characteristics
06/07/1977US4028499 Universal/assigned night answering system for EPABX
06/07/1977US4028498 Private automatic branch exchange system and apparatus
05/1977
05/24/1977US4025729 Telephone ringing control circuits
05/17/1977US4024361 Method of and means for identifying temporarily coacting units in a telecommunication system
05/17/1977US4024349 Quasi-resonant transfer conferencing circuit
05/10/1977US4022991 Conferencing arrangement for use in a PCM system
05/10/1977US4022989 Telephone receiver-off-hook-and-in-use detector
05/10/1977US4022987 Coin telephone station simulator and condition indicator
05/10/1977US4022983 Telephone switching system having automated call hold facilities
05/10/1977US4022981 Conference circuit for pulse coded modulated telephony
05/10/1977US4022980 Ring trip detector
05/10/1977US4022978 Event monitoring transceiver
05/03/1977US4021624 Automatic call generator
05/03/1977US4021621 Automatic group exclusion circuit for a key telephone system
04/1977
04/26/1977US4020473 Automatic system for providing telephone number information service
04/12/1977US4017829 Method and circuit arrangement for testing data processors
04/12/1977US4017696 Initializing circuit
03/1977
03/29/1977US4015091 Telephone ringing generators
03/22/1977US4013956 Telecommunication system with automatically switched modems
03/22/1977US4013839 System for monitoring dialled telephone numbers
03/08/1977US4011413 Hold circuit for telephone
02/1977
02/22/1977US4009347 Modular branch exchange and nodal access units for multiple access systems
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