SHORT-HAUL CARRIER TKLlOnRARH 677 



Break Feature 



When the subscriber opens the loop at the teletypewriter to break 

 transmission coming from the distant tei'minal, a clean-cut space should 

 be transmitted to the line regardless of imy incoming signals. The re- 

 sistor shunted between the plates and cathodes of the receiving tub(\s 

 causes the central office end of the open loop to assume the same potential 

 as the tetrode cathodes. This insures that a steady spacing potential 

 will be applied to the send tube even though the teti'odes are cut off 

 by an incoming space. This provides a rapid, clean break. However, if 

 a large leakage exists across the loop conductors, the resistor will not be 

 able to keep the sending tube in a cut-off condition and a ])reak by the 

 subscriber will result in the incoming transmission being reflected in an 

 inverted condition to the distant carrier terminal. In such a case the 

 distant sending suliscriber would be broken by a "bust-up" of local 

 copy or by operation of the keyboard break lock. This would normally 

 be caused only by a trouble condition in cable loops. 



If a break signal is received over the line from the distant end while 

 the near end subscriber is sending, his loop current is reduced to prac- 

 tically zero. This operates the keyboard break lock thus breaking the 

 subscriber. This circuit differs from the conventional loop circuit in 

 that the receipt of a break signal does not stop the outgoing signals 

 except via the break lock. 



TELEGRAPH DISTORTION 



On quiet circuits, total distortion per section averages 1 to 2 per cent 

 at 60 words per minute and about 5 per cent at 100 words per minute. 

 Plots of received signal distortion versus level of received carrier are 

 shown on Fig. 6 for both signaling speeds. 



EQUIPMENT FEATURES 



The channel terminal employs a formed sheet-metal framework and 

 occupies a space 10| inches high, 5^ inches wide and 7f inches deep over- 

 all. Fig. 7 shows a 43 A 1 channel terminal. It is plug-terminated, and 

 hence removable for maintenance or repair at a bench. 



The basic portion of the channel terminal is common to all frequency 

 allocations. The oscillator network and send filter, which constitute the 

 elements determining the transmitted freciuency, form a plug-termi- 

 nated sub-assembly 7f inches high, 5| inches wide, and 1| inches deep. 

 The receive filter and discriminator, w^hich select the received frequency, 

 form a plug-terminated sub-assembly of the same size. 



