Patent GB-745148-A (GB)
Title: Improvements in or relating to electrical communication systems
IPC: H04M1/26
Filed: 1953-03-06
Abstract: 745,148. Multi-station. systems; impulse transmitters. GILMOOR, A. March 6, 1953, No. 6248/53. Class 40 (4). [Also in Group XXXVIII] A communication system described as for telemetering but said to be applicable to telephone systems comprises stations which can only call and stations which can only be called, selective interconnection being effected at a switching centre by means of relays individual to the called stations and selectable by a uniselector which can be taken for operation by any of the calling stations and set by an ordinary number dial. The completed connection is held under control of normal contacts of the dial. As shown, each calling station can only get connection to particular called stations but it is stated that the system can be modified to make the called stations common to several calling stations. The purpose of the system shown is to connect a meter at the calling position to any one of a number of distant elements indicating a condition-e.g. liquid level. The calling position also includes an indicator which shows which of the called stations has been selected. Normal operation. Dial off-normal springs 101, 103 energize, via a local pilot lamp 89, a relay XA at the switching centre individual to the calling station and a common relay DR which is followed by slow-release relays Z, X and uniselector driving magnet DM. KRA, individual to the calling station, also is energized and also common relays LA, LB. KRA energizes the individual relay TD1A and the common relay B which connects + battery over test relay LT to wiper 58 of the uniselector. DR repeats the dial interruptions S to the magnet DM and relay DH which remains operated during stepping. When the switch stops, the selected relay LR1, LR2, &c. connects up the wanted line. Meanwhile slowacting relay TD1A has energized DX1A and MA. Operation of MA completes a holding circuit for KRA while operation of DX1A releases DR to initiate the sluggish relapse of Z and X. Relapse of X disconnects wiper 58 but the connecting relay remains locked up. LA is released to close a circuit to slow-acting relay TD2A which in turn completes an energizing circuit for DX2A, to de-energize B and complete a holding circuit for the connecting relay. On the relapse of LT when X falls back, the selector goes home. Restoration of dial offnormal springs at the supervisory station provides a holding circuit for KRA through relay N via line 42, substation ground 43a and central station ground 43b. Operation of relay DX2A de-energizes TD1A and hence TD2A but the previously dependent relays MA and DX1A remain operative through holding circuits completed by contacts of KRA and DX2A, and a holding circuit for DX2A is completed through contacts of KRA. Operation of relay N at the supervisory station completes a circuit from the indicator meter 87 through lines 41 and 44 and closed contacts of DX1A and DX2A and line relay LR1 to the remote station, which comprises a power source and a resistor variable with some physical condition. When the reading has been taken a slight movement of the finger-plate as by dialling P (see below) or a new number opens the holding circuits through contacts 101, 102, of LR1, DX1A and DX2A and the system reverts to its original condition. Operation of position check indicator. After the selected connecting relay is operated but before operation of DX2A a resistor R1 &c. associated with that connecting relay is connected in series with the position check indicator 88 at the supervisory station through contacts of DX2A, line 44, contacts N-1 and earth connections 43a and 43b to give an indication characteristic of the selected station. Operation when selected station is engaged. When the wiper 58 stops on the engaged connecting relay contact, test relay LT is shunted by the holding circuit and remains unenergized and when DH falls, the uniselector goes home. If a remote station responsive to one calling station is dialled from another, the appropriate connecting relay is energized but no holding circuit is made for it so that no indication or position check is received. If a dialling operation is effected at one station while the uniselector is in use the circuit through relay XA or XB and DR is incomplete because contacts of X are open so that pilot lamp 89 does not light. Construction of impulse transmitter. This is of the normal dial type except that it is governed to move more slowly and has an additional finger.hole P close to the finger stop for opening the normally closed contacts 101, 102 of the offnormal springs without operating the normally open contacts or the impulsing springs.