Abstract: A speaker of a type having a voice coil wound to a greater length than the length of a magnetic gap into which it extends formed between a pole of a yoke and an annular plate. A magnetic flux density setting structure is provided for establishing a constant value of Bl, where B represents the density of the magnetic flux capable of linking the voice coil and l represents the effective length of the voice coil. The magnetic flux density setting structure may be formed as a tapered surface or surfaces on the pole of the yoke or by a separate tapered plate or plates attached to the annular plate. Further, a metal cap is mounted on the pole covering an upwardly facing cup-shaped body of magnetic material.

Abstract: The apparatus of this invention is a system which is attached to a standard telephone instrument at a receiving station. When a call comes from a transmitting station through a switching station, this call is received in this apparatus, which signals the transmitting station to send its private code. After validating this code, it serves to indicate information about the transmitting station. The receiving station then has the option to answer or not to answer.

Abstract: A telephone call forwarding device enables call forwarding instructions to be given over the telephone for which call forwarding service has been procured from a second telephone line connected to the device. A ring signal detector, in response to a preselected number of rings on the second phone line, causes the second phone line to be seized for a short cycle period in which an authorization signal can be received by the device. If an authorization signal is received during that period, a long cycle timer is activated which maintains seizure of the second phone line for a long cycle period.