Communications

Telephonic Communications

Busy Test Or Make Busy

No:3963874

Busy-test arrangement for electronic private automatic branch exchange

No:4528664

Call progress signal monitor and method for telephone systems

No:3936613

Camp-on detecting system for automatic telephone exchange

No:4320260

Circuit arrangement for determining the connection condition of a subscriber line in a telecommunications network

No:3917910

Circuitry for providing call override in a pbx system in accordance with a supplied class of service

No:6449360

Cleaning method for telephone number list and system implemented therefor

No:5636267

Cleaning system for telephone number list

No:4629832

Communication system administration method and circuitry

No:5428670

Communications marketing system

No:5796816

Device and method for cleaning telephone number list

No:6358519

Germ-resistant communication and data transfer/entry products

No:4166929

Interoffice callback arrangement

No:6879686

Line take-up detection circuit

No:6393123

Method and modem circuit for determining connection status of a phone line

No:6934382

Method for recognizing an off-hook condition on a single subscriber line with two terminal devices

No:5825852

Multisensing circuitry for class signals and stutter dial tone in visual message waiting indicator

No:5355407

Phone busy circuit

No:5805687

Subscriber equipment muting method and apparatus

No:5592529

Telephone inadvertent off-hook condition detector

No:6173040

Telephone line state detecting device

No:5321740

Telephone marketing system