Manual Intercom Line

A 407-type card provides dial intercom service for up to ten stations. Each station is assigned a one digit number from 0 through 9. The dialed station then receives a signal (usually a buzzer) to indicate that it is being called.

The 407-type KTUs only work with dial telephones; they do not support Touch Tone telephone sets.

The 407-type KTUs are eight inch cards with 80 contacts.

The most common 407-type card is the 407C, followed by the 407B and 407A.

Below is the "Condensed Functional Schematic of 407C KTU (Dial Intercom, 10-Code Selector Circuit)" from issue 4 of section 518-215-402 updated in December 1979 from Volume II of the New Jersey Bell Key Systems Service Manual.