5302 tel set - 08/02/10 11:21 PM
When I started with PT&T in the mid 50's ( thats 1950's not 1850's).Our service orders had an area for transmission zone or TZ, if you were in tz 3 you could only use the 302/304 style sets. The 500AB set was to be used in tz 5, the reason was given that if used in tz 3 the transmitter would pack.The 5302 was developed to provide customers a look alike 500 style set. The 500CD was developed with Zener diodes ahead of the transmitter circuit in the network,to shunt high current from the co and not allow the transmitter to pack; plus when the color sets started arriving they could be used in any TZ.
