Patent GB-248941-A (GB)
Title: Improved means for receiving alternating current signals
IPC: H04L27/06
Filed: 1925-04-08
Abstract: 248,941. Pernot, F. E. April 9, 1925. Restoring or modifying imperfect signals; repeating systems using contact-making relays. -In a receiving system for Morse, Baudot, or cable code signals in which alternating currents of low or high frequency cause uni-directional currents to influence a relay responsive to all the code elements, the relay tongue remains in its operative position for a minimum predetermined time irrespective of the duration of the code element. Code elements of longer duration than the minimum code element retain the relay tongue in operative position throughout the duration of the element. The relay tongue may tend to oscillate with the frequency of a series of minimum code elements (e.g. dots) so that a tendency exists to make such elements of uniform duration. On the receipt of a signal. the initial movement of the relay tongue causes a condenser to discharge through an auxiliary winding which increases the torque on the relay. When the tongue reaches the other stop, the condenser charges in the opposite direction, thereby maintaining the tongue in contact with its stop for the full duration of a dot even if the received signal current is of shorter duration. In the system shown in Fig. 1, received signalscause the coil 36, damped by a vane 36, to vibrate contacts 40, shunted by a condenser 44 and. resistance 45, thus producing substantially steady current in the winding 47 of relay A during the receipt of a signal. The relay tongue 50 is connected to a siphon recorder 56 and moves between contacts 50<1>, 50<11> connected to an auxiliary winding 48, condenser 53, inductance 54, resistance 52, 55 and battery 51. The tongue 50 normally rests against contact 50<11>, the condenser 53 being charged. On the receipt of a signal, the opening of contact 50, 50" causes the condenser to discharge through winding 48 in a direction to assist the transit of the relay tongue. On the closure of contact 50, 50<1>, the condenser charges in the reverse direction, the current through winding 48 being in the same direction as before, thus maintaining the contact 50, 50<1> for the proper duration of a dot. At the end of a signal (dot or dash) contact 50, 50<1> opens, and the condenser discharges in a direction to assist the transit of the relay tongue to contact 50<11>, whereupon the condenser is again charged. In the system shown in Fig. 2, the received signals are rectified by the valve 6 and pass through the winding 13 of relay A,. the normal current being regulated by battery 11 and resistance 12 so that the armature 14 normally engages contact 15. An auxiliary winding- 21, condenser 22, and resistances, 23, 24 are connected as shown to the recorder or repeater terminals 25 and batteries 17, 17<1>. The relaytongue normally engages contact 15, condenser 22 being charged by battery 17<1>. On the receipt of a signal, the opening of contact 15 causes the condenser to discharge through winding 21 in a direction to assist the transit of the relay tongue. On the closure of contact 16, the condenser is charged in the reverse direction by battery 17, the current through winding 21 being in the same direction as before, thus maintaining contact 16 closed for the full duration of a dot. At the end of a signal, contact 16 opens; and the condenser discharges in a direction to assist the movement of relay tongue to contact 15, whereupon the condenser is again charged. The steady current through resistance 23 and the lower part of winding 21 tends to shorten received signals which are of greater duration than normal, while the transitory current from the condenser tends to lengthen the effects of currents of shorter duration than normal. The invention may be used with the signalling systems described in Specifications 205,843, 218,361, and 234,529.