Abstract: A rotary dial signal processing circuit and an automatic selecting circuit for combining the rotary dial signal processing circuit with a Touch-Tone digital decoding system. The rotary dial signal processing circuit includes means to interpret line signals as to on/off hook condition, dial pulsing, and completion of a dial pulse sequence. This includes estimation of the time durations of specific signal levels. Thus, for a dial pulse the off-hook signal input goes low for 33-90 ms, causing an appropriate system response; there is no system change for a low input signal of less than 25 ms; a low input signal of over 95 ms is interpreted as on-hook, and causes reset; a high input signal of over 150 ms is interpreted as completion of the dial sequence (timeout). The rotary dial signalling processing circuit counts the sensed dial pulses and provides a 4-bit output code which is compatible with the Touch-Tone code.

Abstract: A multiple-frequency decoder which measures the two-tone output from a multiple-frequency dial type telephone and identifies what number was dialed. A unique binary code is produced as a timed output for each number dialed. In addition, the decoder has provision for detecting and providing as a separate output a unique binary output word whenever a preselected transfer digit, e.g., a 1, 2 or 3 is dialed. With this additional output data, transfer relays can be operated. The decoder inputs are derived from high and low pass filters. The decoder differentiates between valid multiple-frequency tones and extraneous noise, such as voice signals, completely digitally, as follows: once the digital measurement of one cycle of each of the multiple incoming frequencies is made, the combination of all frequency measurements is stored as a k-bit binary word.

Abstract: The present invention relates to a device which is to be used in conjunction with key telephone systems, as for example, intercom systems. More particularly, the invention consists of a device for decoding the pulse output from rotary dial telephones, indicating which digit has been dialed and selectively signalling the called party. Special features include acceptance of a wide range of pulse speeds and ratios with decoding immunity to the initial hookswitch closure and the last opening. The latter permits the digit "1" to be used, providing for an additional signal function. A decoding matrix operates a relay tree with provisions for either single or two-digit codes. The device is intended for use in key telephone systems which include rotary dial telephones.

Abstract: A hold attachment for a single-line telephone to allow the user to replace the handset and resume a call later or at another location. The attachment consists of a non-polarity-sensitive substitution circuit which is connected across the telephone line without regard for line polarity, the circuit including a bridge rectifier, a zener diode, the winding of a holding relay, a light-emitting diode and a manual switch, the contacts of the relay being connected in parallel with the switch. To place a call on "hold", the switch is operated while the handset is placed on hook, and then released. The line voltage causes the zener diode to conduct and energizes the relay, whereby the relay contacts shunt the switch, which maintains the holding connection across the line after the switch is released, and which provides a load resistance such that the switching equipment in the central office will remain held up, maintaining the talking connections to the called telephone.

Abstract: A test unit for testing the wiring connections in modular telephone installations. The unit consists of a housing with an input jack to receive the standard plug used to connect the telephone wiring to a handset. The jack has four terminals, one pair corresponding to the green and red(tip-ring) line wires, and the other pair corresponding to the yellow and black (ground and lamp a.c.) line wires. The tip-ring terminals are connected in the housing through a first diode, a Zener diode and a resistor to a "tip-ring" L.E.D. The a.c. terminals are connected in the housing to a "lamp" L.E.D. through a diode and a transistor, controlled by a network including a blocking capacitor. When the telephone line plug is inserted in the test unit jack, the "tip-ring" L.E.D. will light only if the "tip-ring" line voltage is correct in magnitude and polarity, and the tip ring line conductors have not been interchanged with the a.c. line conductors. The "lamp" L.E.D. will light to indicate proper a.c. voltage on the a.c.

Abstract: In order to distinguish voice and other noise signals which may be present on telephone or similar communications lines from legitimate multi-frequency tone data and control signals, three detectors are disclosed. A frequency drop detector is provided which receives an input from the lines and which provides an output signal upon receipt of any signals appearing on the lines which terminates when the frequency thereof rapidly drops by a predetermined amount. Means consisting of a long-time interval detector are provided for investigating the status of the frequency drop detector's output for a predetermined time after the production of said output signal. If the output signal from said frequency drop detector is provided throughout said predetermined time period, the signal on the lines is defined as legitimate and a circuit output signal is produced. In all other cases, the circuit output signal is inhibited.