Receiver circuit

A receiver circuit for receiving a double current pulse signal from a transmission line and delivering positive pulse or a negative pulse corresponding to that of the double current pulse signal in a discriminating manner. The circuit comprises an input transformer having a secondary winding divided into two halves; a resistor connected in series with each output terminal of the input transformer and having a resistance value which is considerably higher than a characteristic impedance of the transmission line; a diode having a cathode connected to an output terminal of the resistor and an anode connected to ground; and an amplifier having input terminals connected to the resistor and the diode, respectively, and delivering either a positive pulse or a negative pulse corresponding to that of the double current pulse signal in a discriminating manner.

BACKGROUND OF THE INVENTION 
This invention relates to a receiver circuit for receiving a double current 
pulse signal from a transmission line and delivering either a positive 
pulse or a negative pulse corresponding to that of the double current 
pulse signal in a discriminating manner. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a receiver circuit of the kind 
described above which has an input impedance considerably higher than a 
characteristic impedance of a transmission line and which can alleviate a 
load subjected to a double current pulse signal delivered from the 
transmission line. 
A feature of the invention is the provision of a receiver circuit for 
receiving a double current pulse signal from a transmission line, 
comprising an input transformer having a secondary winding divided into 
two halves; a resistor connected in series with each output terminal of 
the input transformer and having a resistance value which is considerably 
higher than a characteristic impedance of the transmission line; a diode 
having a cathode connected to an output terminal of the resistor and an 
anode connected to ground; and an amplifier having input terminals 
connected to the resistor and the diode, respectively, and delivering 
either a positive pulse or a negative pulse corresponding to that of the 
double current pulse signal in a discriminating manner. 
Output terminals of the two amplifiers provided for the two halves of the 
secondary winding of the transformer may be connected to set and reset 
input terminals of a SR type flipflop, respectively, for the purpose of 
providing a receiver circuit having a hysteresis characteristic.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1 is shown one embodiment of a receiver circuit according to the 
invention. In the present embodiment a double current pulse signal shown 
in FIG. 2 is supplied from a transmission line 1 to a transformer 2 having 
a secondary winding divided into two halves whose center terminal 2b is 
connected to ground. 
At a time t.sub.1, a positive pulse is supplied from a terminal 2a through 
a resistor 3a to an amplifier 7a. To an output terminal of the resistor 3a 
is connected a cathode of a diode 4a whose anode is connected to ground. 
At the time t.sub.1, the positive pulse is applied from the terminal 2a to 
the diode 4a which then functions as a high impedance. As a result, a 
positive pulse voltage induced across the terminals 2a and 2b is divided 
by the resistors 3a and 5 and the remainder voltage is applied to the 
amplifier 7a. The input impedance of the amplifier 7a, however, is 
considerably higher than the resistance values of the resistors 3a and 5, 
so that the voltage component divided by the resistors 3a and 5 is 
negligibly small. 
As a result, substantially all of the positive pulse voltage induced across 
the terminals 2a and 2b is applied to the amplifier 7a. A negative pulse 
signal voltage induced across the terminals 2b and 2c is applied to that 
portion of the receiver circuit which is symmetrical to the above 
described circuit portion. To the output terminal of a resistor 3b is 
connected a cathode of a diode 4b, so that a forward voltage is applied to 
the diode 4b which hence functions as a low impedance. As a result, the 
output terminal voltage of the diode 4b becomes substantially ground 
voltage. The resistor 5 and the diode 4b function to produce a very low 
voltage which is then applied to an input amplifier 7b. Hence, the output 
voltage of the input amplifier 7b becomes substantially zero. In this 
case, a pulse signal delivered from the amplifier 7a corresponds to the 
positive pulse of the double current pulse signal supplied from the 
transmission line 1. 
At a time t.sub.2, a pulse signal voltage supplied to the transformer is 
zero, so that the output voltages delivered from the terminals 2a, 2b and 
2b, 2c are also zero. As a result, both the diodes 4a and 4b function as a 
high impedance, respectively. The output voltages delivered from the 
amplifiers 7a and 7b become zero, respectively. 
At a time t.sub.3, a negative pulse is supplied from the terminal 2c 
through a resistor 3b to the amplifier 7b. In the substantially the same 
manner as in the case of the positive pulse, the output voltage of the 
input amplifier 7a becomes zero, while a negative pulse is delivered from 
the input amplifier 7b. This negative pulse corresponds to the negative 
pulse of the double current pulse signal supplied from the transmission 
line 1. 
As stated hereinbefore, in the present invention, to respective output 
terminals of two halves of the secondary winding are connected in series 
resistors and between the output terminals of these resistors and the 
ground are connected diodes, respectively, for the purpose of making the 
input impedance of the receiver circuit considerably higher than the 
characteristic impedance of the transmission line and the forward input 
voltages produced across these diodes are applied to the respective input 
amplifiers. The receiver circuit connected and arranged as above described 
according to the invention has the following advantages. 
(A) The resistors 3a and 3b function as a resistor of a CR filter, so that 
it is possible to make the input impedance of the receiver circuit 
considerably higher than the characteristic impedance of the transmission 
line without requiring any CR filter. 
(B) Respective output terminals of the amplifiers 7a and 7b may be 
connected to set and reset terminals S and R of a SR type flipflop 8, 
respectively, as shown in FIG. 3 so as to provide a receiver circuit 
having a hysteresis characteristic in an easy manner. 
(C) It is possible to deliver positive and negative pulses of a double 
current pulse signal in a discriminating manner. 
(D) The diodes 4a and 4b can prevent the amplifiers 7a and 7b from being 
supplied with a high reverse voltage. There is no risk of the input 
impedance of the receiver circuit being decreased by the presence of these 
diodes. 
The invention is not limited to the embodiments described above, but many 
modification and alteration may be made without departing from the spirit 
of the invention.