These circuits are TTL-compatible, high-speed line receivers. Each is a monolithic dual circuit featuring two independent channels. They are designed for general use, as well as for such specific applications as data comparators and balanced, unbalanced, and party-line transmission systems. These devices are unilaterally interchangeable with and are replacements for the SN55107, SN75107, and SN75108, but offer diode-clamped strobe inputs to simplify circuit design.

The essential difference between the A and B versions can be seen in the schematics. Input-protection diodes are in series with the collectors of the differential-input transistors of the B versions. These diodes are useful in certain party-line systems that have multiple VCC+power supplies and can be operated with some of the VCC+supplies turned off. In such a system, if a supply is turned off and allowed to go to ground, the equivalent input circuit connected to that supply would be as follows:

This would be a problem in specific systems that might have the transmission lines biased to some potential greater than 1.4 V.Read more