Abstract: Each telephone line of a telephone network is individually monitored to determine its on/off hook status and any control pulses or tones being impressed thereon. Each monitor unit when it has information to present generates a first interrupt signal which is fed to a block control unit. The block control unit in turn generates a second interrupt which is fed to a master control unit along with a binary value indicative of the interrupting monitor unit. When the master control recognizes a second interrupt, a CPU interrupt along with a second binary value indicative of the block unit generating the second interrupt is generated. The second binary value (1) provides a block select address signal that enables the interrupting block unit to present to a central processing unit (CPU) data indicative of the interrupting monitor and (2) provides to the CPU data indicative of the block unit to which the interrupting monitor belongs.

Abstract: Method and apparatus for linearizing the response of a mirror galvanometer or the like to a reference driving signal. An optical assembly transmits through a transmission grating a scanned light beam deflected from a reference signal driven galvanometer mirror. The beam passing through the grating is modulated thereby and received by a photocell. The transmission grating modulates the scanned beam in accordance with the velocity of scan of the light beam and the photocell produces an output signal having a freqency content corresponding to the velocity of the beam. An electrical circuit, in response to the frequency content of the photocell output signal, produces a control signal which is combined with the reference driving signal and applied to the galvanometer to deflect the galvanometer mirror in a manner linearly related to the reference driving signal.