Logic select circuit

A monolithic integrated logic select circuit for providing multiple logic threshold signals to an utilization means, comprising:

• first and second circuit means serially connected between a first terminal and a second terminal, said first and second circuit means having substantially identical voltage/current transfer characteristics wherein a first logic threshold signal of a first level is produced at the interconnection between said first and second circuit means when an operating potential is applied at said first terminal, said first logic threshold signal having a magnitude substantially equal to one-half said operating potential, said second terminal receiving a ground reference potential;
• current source means for supplying a current of predetermined magnitude to said second circuit means wherein a second logic threshold signal of a second level is produced at the interconnection between said first and second circuit means whenever said first terminal is open-circuited;
• output circuit means coupled to the interconnection between said first and second circuit means for supplying said first and second logic threshold signals to the utilization means;
• and
• said first circuit means including a first diode, a second diode and a first resistor serially connected between said first terminal and a circuit node, said circuit node being coupled to said output circuit means.