706 BELL SYSTEM TECHNICAL JOURNAL 



signals and a bell for announcing incoming calls. A special handset 

 with push button completes the control unit assembly. 



At Boston, the marine radio telephone traffic is handled at two 

 positions on the outgoing toll board especially modified for this pur- 

 pose. The wire lines from the Green Harbor station terminate at this 

 point, and calls from vessels can be switched by the operator to any 

 point connected to Bell System facilities. The normal wire lines are 

 three loaded cable pairs. One pair is used for transmission from the 

 shore telephone to a boat, the second conducts speech received from a 

 boat through the toll position to the land line telephone, and the third 

 is employed as an order wire for communication between the operator 

 at the marine position and the technical operator at the Green Harbor 

 station. All of these circuits are duplicated over an alternate route 

 for use in case of trouble on the normal facilities. 



The marine operator dials the code assigned to the vessel desired. 

 The dialing operation produces the desired grouping of 600 and 1500 

 cycle pulses which modulate the radio transmitter carrier frequency 

 of 2506 kilocycles. The signaling unit on the vessel is actuated by 

 these pulses and the bell rings. The captain raises the handset from 

 the switch hook on the control unit, presses the push button in the 

 handle of the handset and announces the name of his vessel. The 

 operator then completes the connection and the conversation takes 

 place. 



In placing a call from boat to shore the captain or member of the 

 crew raises the handset from the switch hook and, after listening to 

 ascertain that no conversations are in progress, presses the push button 

 and calls "marine operator." The marine operator who is normally 

 monitoring on the channel ascertains the name of the calling vessel, 

 the shore station desired and other necessary details, and while the 

 calling party holds the line proceeds to call the land line telephone and 

 establish the connection. 



When a person on one boat wishes to talk with a person on another 

 boat, the procedure in placing the call and establishing the connection 

 is the same as in the case of a ship-to-shore call, except that when both 

 are prepared to talk, the technical operator at Green Harbor operates 

 a by-pass key which connects the radio receiver output and radio 

 transmitter input without including the voice operated device and 

 other equipment associated with the land circuits. The land line is 

 bridged onto the circuit so that the marine operator may be advised of 

 any difficulties which arise in carrying on the conversation. 



During the more than two years that the system has been in experi- 

 mental service, the transmission results up to distances of 500 miles 



