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US 4,394,543 AGranted
Telephone line holding circuit
AssigneeLear Siegler, Inc.
InventorsFrancis P. Keiper, Jr., John N. Kerns
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AssigneeLear Siegler, Inc.
InventorsFrancis P. Keiper, Jr., John N. Kerns
Estimating the term…
A telephone line holding circuit is disclosed which is adapted for temporary connection across a telephone line to maintain that line in a hold condition while line measurements and tests are being performed. The holding circuit is designed to be used over a wide range of line supply voltages and line resistances without introducing line measurement errors. The holding circuit includes a current regulator which maintains the line current at a predetermined level as long as the voltage appearing across the line remains above a predetermined voltage level. The holding circuit also includes a voltage regulator which reduces the predetermined current level to a value which prevents the average line voltage from being reduced below the predetermined voltage level. The holding circuit further includes circuit elements for protecting the circuit elements from damage caused by the application of excessive voltage on the line.
A holding circuit adapted for connection across a telephone line which has a voltage across the line and a current flowing through the line when held, said holding circuit being adapted to maintain the line on hold, said holding circuit comprising:
Dependencies are inferred from the claim text.