AUTOMATIC TOLL SWITCHING SYSTEMS 8G1 



switching points is based on the Toll Crossbar System now in service 

 and has been constructed by the addition of the necessary CSP features 

 to the basic structure of that system. 



FUNCTIONS OF THE CSP SWITCHING SYSTEM 



The system is designed to be suitable for location in either a step-by- 

 step or a panel-crossbar local area. In addition to the functions required 

 for operation as a CSP, it must, of course, perform the normal toll switch- 

 ing functions required of any system for swit(^hing the toll traffic charac- 

 teristic of the locality it serves. These may be stated very briefly. 



Ordinary Toll Switching Functions 



1. It accepts calls either directly from operators or from senders in 

 distant offices. In the interest of economy it accommodates itself to the 

 signaling language the operator's position or sender is equipped to deliver. 

 Calls from operators may be either in the dial pulse (DP) or multi- 

 frequency^ (MF) form. Calls from senders will be in the MF form. 



DP pulsing is the decimal type delivered directly by the dial and is 

 at the rate of about one digit per second. MF pulsing represents a 

 particular digit by a combination of two out of five frequencies in the 

 voice range; it uses one of these frequencies in combination with a sixth 

 frequency to produce a signal indicating the beginning of pulsing, and 

 a different one of the five in combination with the sixth for an end of 

 pulsing signal. It is transmitted from senders at the rate of about seven 

 digits per second. Operators usually key at the rate of up to two per 

 second. 



2. The toll switching system completes calls to various types of me- 

 chanical toll and local offices and to operators, using the form of signaling 

 dictated by economy for each call. For distant toll offices and local offices 

 using step-by-step equipment DP will be transmitted, for other CSP's 

 and usually for local crossbar offices MF will be transmitted and at 

 manual toll offices an operator will be called in either automatically on 

 seizure of the toll line or by sending a ringing signal over the line, but 

 no pulses will be transmitted. Forms of pulsing different from cither of 

 these are used for local panel offices and for local manual offices in 

 panel-crossbar areas. 



3. It must transmit signals in one direction for initiating, holding and 

 releasing the connection and in the opposite direction to indicate to the 

 originating end when the called subscriber answers and hangs up. These 



