Patent GB-854562-A (GB)
Title: Electric pulse signalling systems
Inventor: WARD HUGH JENNINGS
IPC: G08B1/08
Filed: 1958-12-12
Abstract: 854,562. Electric selective signalling. STANDARD TELEPHONES & CABLES Ltd. Dec. 12, 1958, No. 40170/58. Class 40 (1). In a system for signalling to a central station the state of a number of pieces of apparatus at a remote station, the remote transmitter and the central receiver each consist of relay switching circuits and each has a multivibrator consisting of a pair of inter-connected relays which maintain in synchronism uniselectors at the remote and central stations, the signals being characterized by a change from positive to negative or vice-versa. In Figs. 1 and 2 all relays with more than one winding are shown in the " mark " condition, the arrows indicating the direction the marking current flows in each winding. All singlewinding relays are shown in the released condition. Transmitter.-When the control key, Fig. 1, is operated, negative voltage applied to the line picks relay SR, Fig. 2, the contacts sr1 of which transfer to the s (space) position to de-energize the locking coil of relay SY to allow it to pick through current in the third coil. This relay and relay SX form a multivibrator which oscillates by transfer of contact syl as long as the locking coil is de-energized, and at each oscillation causes a uniselector SW to be moved one step so as to test a unit of apparatus connected to one of the contacts 1-6. The multivibrator relays are so designed as to spend about onethird of the oscillation time in the " space " condition (relay SX picked) and two-thirds in the " mark " condition. The cycle is represented in Fig. 3 as divided into three periods. The uniselector stepping coil SW is energized through contacts ss1, relay SS being controlled through contacts of relay SX. The wiper steps to the next position, as shown in Fig. 3, when the stepping-coil SW de-energizes. Contacts sn2 and sp3 can connect to positive or negative supply and contact ss4 determines which shall be connected to line at point A. Where the uniselector wiper stands on a contact connected to a closed contact, e.g. SUP3 (indicating the condition of a unit of apparatus) the closure of contacts ss2 will energize relay SP (see Fig. 3). This causes the point A to become positive through transfer of contacts sp3. When theuniselector wiper stands on a contact (e.g. contacts 1 and 2) whose associated contact is open, the relay SP is not operated. In this case the signal sent is due to the picking of relay SS in the third period and takes the form of a positive pulse through contacts sn2. When relay SX drops out, relay SS is de-energized and contacts ss4 return to the position shown in Fig. 2 where a negative voltage is applied to the line. The signal therefore consists of a change from negative to positive at the third period of the cycle followed by a change back to negative so that the next cycle, if it is to be the same, can again start with a negative voltage. The signal condition at A for three successive cycles are shown in Fig. 3, relating respectively to uniselector contacts 0, 1 and 2, the signals transmitted in any cycle being related to the contact engaged by the uniselector in the preceding cycle. When the uniselector engages contact 3 relay SP is energized in the third period described above and relay SN operates, holding itself in through contact sn1 until de-energized at the end of period 11, Fig. 3. This means that when contact ss4 switches to the mark position at the beginning of period 10 the signal at A remains positive for the next two periods owing to the transfer of contacts sp3. At the beginning of period 12 the contact ss4 reverts to the space position and since contacts sn2 are transferred a negative signal is applied to line. The next cycle (5) continues with two negative periods changing to positive in the third. Receiver.-A multivibrator at the receiver consists of relays CY, CX, Fig. 1, connected for oscillation, spending one period in the mark condition and two in the space. Relay CR responds to the positive signals on the line and causes the multivibrator to make one oscillation by transferring contact cr1. This simultaneously releases relay CP so that contact cp3 closes and contact cr1 transfers to space before contact cr1 moves to space. Closing of contact cp1 energizes slow-to-release guard relay CG which remains operated during openings of contacts cp1 and cn1. After period " 0 " the relay CR releases, contact crl returns to mark position and when contact cxl closes, relay CP operates and the multivibrator is locked by the current in the third winding of relay CY. Contact cg1 is transferred so that when contact cp2 closes the driving magnet CW of the uniselector is energized. The uniselector steps to contact 1 when it is de-energized at the end of period 2, when relay CR operates to release relay CP. In period 4 the relay CR reverts and contact cr1 moves to mark position so that when contact cr1 closes relay CP and drive magnet CW are energized as before. Since contact cn4 remains open, a relay similar to relay C3A remains unoperated and a green lamp corresponding to contact 1 remains lit. When the signal corresponding to contact 3 arrives (in period 10) the relay CR remains operated and its contact cr1 remains at space so that when the contact cx1 returns to mark, relay CN operates. Contact cn4 being closed, relay C3A is operated and holds over contact c3a1. A red lamp is lit through contact c3a2 indicating the condition of the apparatus connected to contact 3 of the sending station. Drive magnet CW is energized for the next step by contacts cn2 and the process continues for each step of the uniselectors in turn. Specification 851,398 is referred to.