Communication Mfg. Co.

Micron Communications, Inc.

Communication Manufacturing Co.

Orrin B O'Dea

An electronic relay circuit for replacement of an A-type relay in a step-by-step selector and connector of a telephone exchange system is implemented with a first operational amplifier (10) connected to the tip (T) and ring (R) conductors of a telephone line, and a second operational amplifier (24') with hysteresis for use as a comparator. A capacitor (C1) with a diode (D1) in parallel couples the input terminal of the comparator to a reference voltage from a voltage divider (R1, R2) in order that signal transitions from the input amplifier appear as common mode signals for a period determined by the RC time constant of a coupling resistor (R3) for ON-HOOK to OFF-HOOK transitions limited in amplitude by the parallel diode (D1) and the RC time constant of a resistor (R4) connected to a source of negative voltage for OFF-HOOK to ON-HOOK transitions limited in amplitude by a series diode (D2). A diode (D3) in series with the voltage divider introduces a compensating voltage drop for the diode (D2). The first amplifier is provided with a low-pass band of at least twice the dialing frequency (15 Hz).

Electronic telephone relay

First and second indicating circuits connect a source of ternary pulses to a load. The ternary pulses are subject to baseline overshoot above a threshold level for a given period of time after the termination of each pulse. The first indicating circuit transmits an indication to the load responsive to ternary pulses of positive polarity above the threshold level. The second indicating circuit transmits an indication to the load responsive to ternary pulses of negative polarity above the threshold level. Transmission of an indication to the load by the second indicating circuit is inhibited for the given period of time after the termination of a ternary pulse of positive polarity above the threshold level to suppress negative baseline overshoot. Transmission of an indication to the load by the first indicating circuit is inhibited for the given period of time after the termination of a pulse of negative polarity above the threshold level to suppress positive baseline overshoot. The load is preferably an up-down counter that senses errors in the ternary pulse pattern. The indicating circuit each include a normally nonconducting switching transistor, inhibited by clamping circuits which are controlled by cross coupled feedback paths having a significant transmission delay relative to the duration of the ternary pulses, but smaller than the minimum interval between successive ternary pulses. In one embodiment, the level of the ternary pulses is sensed by a light emitting diode optically coupled to a photo resistor, which shunts the source for purposes of automatic gain control. In another embodiment, a bias turn-on switch is actuated when a minimum pulse level occurs.

Overshoot suppression circuitry for ternary pulses

Disclosed is a telephone system test apparatus for a telephone switching system having tip and ring circuits which cause a control relay to close upon completion of a path therebetween and which cause the same relay to close upon further opening and closures of the path between the tip and ring circuits. Means monitors such a telephone system for detecting a preselected operative condition therein. Means detects a predetermined impedance condition across such tip and ring circuits. A dial pulse loop circuit is coupled across such tip and ring circuits and it normally has a high impedance condition. Means selectively switches a first low impedance condition around the dial pulse loop circuit upon detection of such predetermined impedance condition and thereby applies a margin test to the first relay. Means opens and closes the dial pulse loop circuit one or more times for applying dial pulses across the tip and ring circuits upon detection of the proper operating conditions and the non busy condition. Means switches a second substantially lower impedance, than the first low impedance, around the dial pulse loop intermediate each opening of the dial pulse loop to thereby ensure proper operation of the control relay.

Relay margin test set

A test apparatus for forward selector switches in a telephone switching system having a telephone loop. Means detects a preselected operative condition in such telephone systems. Means generates a variable number of pulses for control of forward selector switches. The latter includes the following: A switch for closing and breaking a telephone loop to thereby form such a pulse; an indicator for indicating the desired number of pulses including one or more than one pulse; a counter; means for enabling the counter to count the formed pulses greater than one; a control circuit enables the switch to break a telephone loop upon such detection of a predetermined operative condition and for each different state of the counter, and the control circuit is also operative for terminating the breaking by the switch upon a predetermined relation existing between the indicator and counter. Also disclosed is a pulse generating means as a subcombination of the aforementioned.

Telephone switching system test set

A coin telephone station simulator and condition indicator. Separate tip, ring, and ground input/output conditioners are provided for connection to a telephone system for test. A controllable coin present relay simulator circuit is switchable from a first high impedance condition to a second lower impedance condition in between tip and ground conductors. A coin test switch switches the controllable relay simulator circuit from the first to the second condition. A coin present indicator is provided together with means for energizing the coin present indicator when the simulator circuit is in the second lower impedance condition. Coin collect and coin return indicators are provided. A coin collect and return detection circuit is responsive to first and second electrical signals, of opposite polarity, momentarily and separately applied in between the tip and ground conductors for individually energizing, respectively, the coin collect and coin return indicators. Low, acceptable and high voltage indicators are provided. A line voltage detector circuit is responsive to an electrical signal applied between the tip and ring conductors of below a first voltage level for enabling the low indicator and is responsive to a signal above a second voltage level for enabling the high indicator and is responsive to a signal with a voltage level of in between the first and second levels for enabling the acceptable indicator.

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Garden Grove, CA, United States of America

Orrin B O'Dea