Automatic telephone loaded/nonloaded facility type identification circuit

A transmission network of a type adapted to couple a receive unidirectional transmission path and a transmit unidirectional transmission path to a bidirectional transmission path including,

• transformer means for coupling the bidirectional transmission path in circuit relationship to the receive path and the transmit path,
• canceler circuit means in circuit between the receive path and transmit path for generating a correction signal to be algebraically combined with a transmit signal for canceling an error signal developed in the network when the bidirectional path is connected to said transformer means,
• means for controllably connecting said canceler circuit means in and out of circuit between the receive and transmit paths,
• means for controllably generating and supplying to the receive path a test signal having a predetermined frequency and a predetermined amplitude,
• means for detecting signal amplitude in the transmit path,
• means for comparing said detected amplitude to a predetermined threshold value, said comparing means generating a first prescribed signal if the detected amplitude is greater than said threshold value and generating a second prescribed signal if the detected amplitude is less than said threshold value, and
• control means for generating control signals to control operation of said signal generation means and said canceler circuit connection means, said control means being responsive to said first or second prescribed signals to generate signals for connecting a loaded type canceler circuit of a nonloaded type canceler circuit, respectively, in circuit between said receive and transmit paths.