Abstract: A standard T-1 span is connected to a digital central office or remote terminal. Telephone equipment for such a T-1 span defines a superframe format with each frame of the twelve frames of a superframe having twenty-four eight-bit position time slots. Telephone system signalling requires T-1 signalling bits be located in the least significant bit position of each time slot in every sixth frame. In the disclosed system, simultaneous digitized voice and data share a single time slot for transmission along with the T-1 signalling bits in that time slot. In order to achieve the additional capability, the disclosed system employs least and next-to-least digitized voice bit swapping and a data bit occupying the space of the swapped least significant digitized voice bit, which bit is deleted.

Abstract: A brush assembly for cleaning the bore of a cannon. The assembly includes a cylindrically-shaped brush (46) supported on front and rear plates (22, 24). An assembly shaft (30) extends through the plate, the center of the brush and through the rear plate. A threaded collar (36) is connected to the rear of the assembly shaft for receiving a ramming shaft (42). A conically-shaped centering element (58) is disposed over the threaded collar and is provided with an opening for accommodating the ramming shaft. The centering element realigns the brush with the bore thereby permitting the brush assembly to be pulled back through the barrel (72) without the necessity of manually recentering the assembly with the bore.

Abstract: An intercom system for a key telephone installation which can be expanded and contracted to service a diverse number of subscriber units. The intercom system is expandable on a modular basis of eight subscriber units. The preferred embodiment can service up to forty-eight subscriber units. The intercom hardware includes a single supervision module, at least one signalling module, and one or more station modules. The intercom system provides up to six independent communication links for a forty-eight unit system. The system also provides such features as dial tone, ring-back tone, busy signal, interrupted ringing, and independent ringing. These features are provided by a hardware organization that is both expandable and comparatively inexpensive.

Abstract: Privacy by way of excluding all other key set talking circuits (T-R) from the seized line in a standard key set or conference key set system is obtained by providing a privacy exclusion circuit at each key set in the system. The exclusion circuit at the key set which seizes a particular T-R line first causes the voltage on the A lead associated with that line to drop below a certain critical value, thereby causing all the other exclusion circuits in all the other key sets to open their respective talking circuits if an attempt is made to access the occupied line. In order to permit other key sets to access the occupied line, the key set first to seize the line can, without relinquishing the line, permit the voltage on the respective A lead to rise above the critical value, permitting another key set access. Upon such access occurring by the other key set all other key sets are again excluded because the voltage on that particular A lead again drops below the critical value.

Abstract: In areas utilizing telephone switching equipment that will only accept dial pulses, a conversion unit, that fits into the space formerly occupied by the dialing mechanism in a standard telephone subscriber's unit, provides touch-pad dialing. The conversion unit accepts input signals, representing digits, from a standard 3 .times. 4 matrix touch-pad at an asynchronous rate and starts out-pulsing at the required pulse repetition rate as soon as the first digit signal is received. During each touch-pad button depression, an audio tone is supplied to the subscriber unit earpiece. The conversion unit provides for programmable toll restriction that permits selective prohibition of out-pulsing at each subscriber unit. At the instant a restricted input signal is received, the conversion unit provides a steady audio tone to the earpiece and stops out-pulsing. To prevent hookswitch dialing, the conversion unit extends the break period of the electronic pulsing switch.

Abstract: To prevent clandestine listening devices located in a key telephone subscriber station from utilizing the tip and ring leads of the subscriber station as a transmission path out of the subscriber's building, the subscriber station tip and ring leads are open circuited at the line card circuit during an on-hook or hold condition. Besides isolating the tip and ring leads from the subscriber station during hold and on-hook, the security line card circuit prevents high frequency signals from propagating down the telephone line when the subscriber station is on-hook. The security line card circuit allows the subscriber to exercise full supervisory control over the telephone lines and includes circuitry that controls the operation of audible and visual indicators of the associated key telephone.

Abstract: Transfer of an incoming call on a first telephone line for a first subscriber set to a second, independent telephone line for a second subscriber set is accomplished without permitting a party at the first subscriber set to listen to the transferred call. An adjustable time delay circuit causes the tip and ring leads of the first central office telephone line to be switched to the second subscriber set, after a predetermined amount of ringing at the first subscriber set. If the second subscriber set is in use or is being rung at the time a transfer is to take place, no switching occurs. If the first subscriber set is answered before the preset time delay is elapsed, no switching occurs. The line transfer circuit may operate from either a -24 or -48 volt DC supply.

Abstract: An improved line card circuit usable with key telephone systems is adapted to permit a message to be automatically transmitted from a subscriber key telephone station when operated to place a telephone line in a hold condition. A coupling circuit interfacing the message source and the telephone line during the hold condition of the line provides a high degree of cross-talk isolation. The coupling circuit also has the feature of automatically limiting to a predetermined level the power of the output signal supplied to the telephone line. A strappable option is provided by the coupling circuit to permit its operation with a standard eight ohm high fidelity amplifier source as well as with a 70 volt intercom systems. The line card circuit, besides these features, includes circuitry to allow full supervisory control of a telephone line to be exercised by a user of the subscriber key telephone when such unit is not in the hold condition.

Abstract: A solid state interrupter is described for controlling the visual and audible indicators in telephone systems and more particularly to control the line selection lamps and electromechanical ringers in key telephone sets. The interrupter includes switching means individually connected between a pair of lamp wink terminals, a pair of lamp flash terminals and a pair of ring signal terminals. Each of the switching means includes a control circuit for alternately enabling and blocking the flow of current in the circuit between the associated terminals in response to the application of a predetermined control signal to the control circuit thereof. An oscillator is provided for generating an a.c. reference signal. Suitable dividers and gates are connected between the oscillator and the control circuits of the switching means to control the duty cycle and frequency at which a circuit path is made between the associated terminals.

Abstract: A message waiting transfer circuit for use in a telephone system is described. An attendant telephone set is arranged to monitor the calls received by a plurality of principal telephone sets. The attendant set includes a receiver (and transmitter) and a separate line or principal set selection key associated with each principal set in the system. Actuation of a selected line selection key and the removal of the receiver from its cradle or switch hooks at the attendant set seizes the telephone line conductors (pair) associated with the selected principal set to enable the operator at the attendant set to answer an incoming call, etc.. The attendant set includes a message control key for providing a message waiting signal to any selected principal set. A separate message waiting transfer circuit is connected between each principal set and the attendant set.