Patent GB-762289-A (GB)
Title: Improvements in staff locator systems
IPC: G08B3/10
Filed: 1954-02-04
Abstract: 762,289. Selective signalling. INTERNATIONAL BUSINESS MACHINES CORPORATION. Feb. 4, 1954 [Feb. 7, 1953], No. 3311/54. Class 40 (1). In a staff locator system in which search impulses of different lengths corresponding to different persons are sent to actuate, selectively indicators at a remote receiver station, the search impulses are produced by constantly driven cams selected for operation by switches associated with the respective persons, the search impulses determining the angular rotation of a contact arm at the receiver driven for the pulse duration in synchronism with the transmitter cams. The impulses are sent over the transmission line of a master and slave clock system. A staff locator key may be actuated at any time but the corresponding search impulse is initiated only during an interval between clock impulses. Several locator keys may be actuated together, the search impulses then being sent successively in the order of their lengths. Several search impulses may be sent between consecutive clock pulses. Transmitter, Figs. 1, 2. When the master clock sends its normal minute impulses (except for the 59th minute when supervisory impulses are transmitted) it closes contacts NU, SU to energize a magnet M which unlatches a cam StN1 permitting a continuously running synchronous motor SM1 to drive the cam shaft W1 through one revolution in 58 seconds when the shaft is locked until the next minute clock impulse. The shaft W1 drives a cam shaft W2 at an integral multiple higher speed, shaft W2 carrying cams N1 ... N4, corresponding, respectively, to staff selector keys X1 ... X4 (not shown) and a further cam StN3. Depression of any selector key operates a corresponding relay T1 ... T4, Fig. 2, but has no other effect until the cam StN3 passes through its normal position, shown, when a relay ST is operated, locks, and energizes a relay J over the cam StN2. When the cam shaft W2 has moved off-normal sufficiently for a minute clock pulse, transmitted at this time, to have ceased, negative at St1 is fed over the cam contact K1 ... K4 corresponding to the actuated selector key, contacts tl,-2, t2,-2 ... of the operated relay T1 ... T4, a resistor W, terminal H, and contact j2 to line to initiate the search impulse. The impulse persists until the notch a in the operative cam N1 ... N4 is reached, the impulse durations being made different for each cam. As the search impulse circuit is broken by the operative cam contact K1 ... K4, a relay S1 ... S4 corresponding to the depressed key is operated and locks. When the contact K1 ... K4 of the operative cam leaves the notch a, the impulse circuit to the receiver is again closed to zeroize the receiver selector switch (see below). At the end of a cycle of the cam shaft W2 a rise b on the operative cam functions to energize a relay R1 ... R4, corresponding to the operative key X1 ... X4 and locks, until the key in question is released when the transmitter selector relays revert to normal. A reset key TL12 may also be operated to zeroize the relays S. The reset key in addition connects negative to line, via contacts TL11 and terminal H, to send a " strong " reset pulse. Simultaneous operation of selector keys. Although several keys X1 ... X4 (not shown) may be depressed together, only one of the relays T1 ...T4, Fig. 2, can be operated at a time, so that the respective search impulses are sent in turn. For example, if X1, X3 are depressed together, relay T3 cannot, operate so that key X1 takes precedence and the search impulses corresponding to the two keys are sent in succession. Further, if a locator key is depressed subsequently to another key corresponding to a longer search impulse, then the key corresponding to the shorter search impulses takes over control of the line pulse duration, the longer search pulse being sent subsequently. A lamp L at the transmitter flashes for the duration of clock impulses, i.e. while relay J is off. Receiver, Figs. 3, 9. The positive minute clock pulses are fed over contacts mk, j2 and line A, Figs. 1, 3, to the slave clocks NU1, NU2, Fig. 3, in series with rectifiers Z1. The negative search pulses over line A are fed directly to the receiver E1 in series with a rectifier Z2. The receiver E1 consists of two parallel connected marginally operated relays O, P, Fig. 7 (not shown). Relay O only responds, due to the resistance W in the impulse circuit, and starts a synchronous motor SM2, Fig. 9, which drives rotary selector brushes B1, B2 until the cessation of the search impulse when the motor SM2 stops in a position corresponding to the duration of the search pulse, and over brush B1, a relay U1 ... U4 and lamp L1 ... L4 corresponding to the selected key is operated. The operated relay U1 ... U4 locks and maintains the selected lamp L1 ... L4 flashing. A relay Q, energized over brush B2 and its associated contacts, gives an acoustic signal for the search impulse duration, this signal being repeated at greater intervals under the control of bi-metallic interrupting relays Bi1, Bi2 as long as one of the relays U1 ... U4 is operated. When the negative line impulse is resumed, as above described, the motor SM2 advances the selector brushes to zero, a contact esgment sm coacting with brush B2 to effect accurate zeroizing. The indicating lamps L1 ... L4 are extinguished by the reset "strong" negative pulse over the line which is sufficient to operate the receiver relay P, Fig. 7 (not shown), which releases the operative relays U1 ... U4 and stops the motor SM2. Simultaneous operation. With simultaneous key operation as above described the operative lamps L1 ... L4 are brought into operation successively. Once a located person has reported, his key is restored to normal, and the reset pulse sent as above described. All lamps are extinguished and the motor SM2 stopped, but the lamps of the other persons to be located will flash on again after one cycle of cam shaft W2. Modifications. The locator system may be associated with a two-wire self-supervisory clock system, Fig. 4 (not shown), a clock system where the clock impulses alternate in polarity, Figs. 5a, 5b, 6 (not shown) or control circuits for a slave clock system, Figs. 10-13 (not shown).